Rewrite TODO.md sentence by sentence (closes #135 )

TODO.md is the project's own task list, judged by the same rules as README.md: short sentences, lists as bullets, nothing a newcomer reads twice. Every completed step is kept with its date and issue, in fewer words. The 2026-07-22 policy-compliance checklist is folded into the step that did the work, and the accepted divergence from the layout policy gets a section of its own. Workflow, Status and Next Step keep their rules unchanged. Model: fable-5-1
2026-10-26 06:20:08 +00:00
14 changed files with 1376 additions and 2373 deletions
@@ -14,208 +14,130 @@
 # Status
 - Pre-1.0.
- The tracker is authoritative for the pre-1.0 backlog. The open issues under
+- The tracker is authoritative for the backlog. The open issues under the
-  the `1.0.0` milestone are what remains before the tag. This file records
+  `1.0.0` milestone are what remains before the tag. This file records history
-  history and process, not the queue.
+  and process, not the queue.
 # Next Step
- Take the next issue from the `1.0.0` milestone,
+- Take the next issue from the `1.0.0` milestone:
  https://git.eeqj.de/sneak/sfdupes/milestone/17. The issues are not restated
  here, because a copy drifts as soon as the tracker moves.
 # Completed Steps
-Newest first. An entry ends with its date and its issue or branch, where those
+Newest first. Each entry ends with its date and its issue or branch.
 are known.
- `TODO.md` rewritten from scratch by the same rules as `README.md`, sentence by
+- `TODO.md` rewritten from scratch by the same rules as `README.md`: short
-  sentence. Every completed step is kept, with its date and its issue or branch.
+  sentences, lists as bullets, nothing a newcomer reads twice. Every completed
-  The policy-compliance checklist of 2026-07-22 is folded into its step
+  step is kept, with its date and issue, in fewer words. The policy-compliance
-  (2026-11-02, https://git.eeqj.de/sneak/sfdupes/issues/135)
+  checklist of 2026-07-22 is folded into its step (2026-10-26,
  https://git.eeqj.de/sneak/sfdupes/issues/135)
 - `README.md` rewritten from scratch, sentence by sentence, as a newcomer reads
  it. It leads with what the program is and how to use it. A reference section
-  covers every setting and every subcommand. Development and testing come last.
+  covers the settings, the database, the output formats and the exit codes;
-  Every statement was checked against the code on `next`. Five comments in
+  development and testing come last. Every statement was checked against the
-  `main_test.go` cite "Settings", where their rules now live. One comment each
+  code on `next` (2026-10-26, https://git.eeqj.de/sneak/sfdupes/issues/135)
  in `scan_test.go`, `trees_test.go` and `exclude_test.go` cites what the README
  now says (2026-11-02, https://git.eeqj.de/sneak/sfdupes/issues/135)
 - Each record holds `disk_size`, the bytes the file takes on disk. That is its
  allocated blocks, `st_blocks` × 512, from the `lstat` call the walk already
  makes. `trees` prints a `disk_size` column after `size`. It is the sum over
  the `dupe` copy's files. On a compressed or sparse file `disk_size` differs
  from `size`. A rescan updates the `disk_size` of an unchanged file whose size
  on disk changed, without reading the file (2026-10-27,
  https://git.eeqj.de/sneak/sfdupes/issues/147)
 - The database keeps the number of records and the sum of their sizes in the one
  row of a `totals` table. Three triggers on `files` keep that row current.
  `info` reads that row. So do `scan`'s `load` phase and the `read` phases of
  `report` and `trees`, for their totals. No count reads every record any more.
  The triggers make each write to `files` slower. `scan` keeps SQLite's
  temporary data in memory. That wins back part of that time (2026-10-27,
  https://git.eeqj.de/sneak/sfdupes/issues/146)
 - an operand at or inside a directory named `.zfs` is never scanned, whether
  given alone or under another operand. `scan` warns about it, counts it as
  skipped and does not walk it (2026-10-26,
  https://git.eeqj.de/sneak/sfdupes/issues/142)
 - A file or directory removed while the scan runs is not an error, in the walk
  or in the hash phase. The scan prints no line for it and does not count it as
  skipped. When the first of several hard links to a file is gone, the hash
  phase reads the next one instead. On a terminal every progress display starts
  with the spinner, the hash phase's included. A phase with an exact total ends
-  its line with its percent and a 10-column bar at the terminal's right edge.
+  its line with its percent and a 10-column bar at the terminal's right edge,
-  The bar no longer moves as the line's length changes. A line too wide for the
+  which no longer moves as the line's length changes. A line too wide for the
  terminal now loses its rate before its bar. The time remaining is labelled
  `remain`, not `eta` (2026-10-26, https://git.eeqj.de/sneak/sfdupes/issues/133)
 - The `head`, `tail` and `content` columns are BLOBs, each holding the raw 32
-  bytes of a SHA-256. That is half the size of the hex text they held. The
+  bytes of a SHA-256, half the size of the hex text they held. The hashes stay
-  hashes stay raw from the hash phase through the database to `report` and
+  raw from the hash phase through the database to `report` and `trees`. Reading
-  `trees`. Reading a record whose hash is not 32 bytes is an error (2026-10-26,
+  a record whose hash is not 32 bytes is an error (2026-10-26,
  https://git.eeqj.de/sneak/sfdupes/issues/134)
- The hash phase gives three hashes to every file that the walk records. `head`
+- Every file the walk records gets three hashes in the hash phase. `head` and
-  and `tail` are the SHA-256 of its first and last 64 KiB. `content` is the
+  `tail` are the SHA-256 of its first and last 64 KiB. `content` is the SHA-256
-  SHA-256 of the whole file under 100 MiB, and of 1 MiB at each gigabyte from
+  of the whole file under 100 MiB, and of 1 MiB at each gigabyte from 100 MiB
-  100 MiB up. Gone are:
+  up. The 10 MiB and 50 MiB thresholds, the size census, the records without
-    - the 10 MiB and 50 MiB thresholds;
+  hashes and the content phase are gone. A scan has four phases, and a rescan
-    - the size census, which counted the sizes of every walked file and of every
+  reads only new and changed files. `info` no longer counts the records with
-      record outside the operands. A file was hashed only when the census showed
+  hashes, since every record has them (2026-10-25,
-      another file of its size;
+  https://git.eeqj.de/sneak/sfdupes/issues/132)
    - the records without hashes;
    - the content phase.
-    A scan has four phases, and a rescan reads only new and changed files.
+- `REPO_POLICIES.md` and the four scripts that pass `CACHEBUST` re-vendored from
-    `info` no longer counts the records with `head` and `tail` hashes, nor those
+  `sneak/prompts` `next` at `0653579`. The module download in the `lint`, `test`
-    with a content hash, since every record has all three (2026-10-25,
+  and `builder` stages of the `Dockerfile`, and the package install in
-    https://git.eeqj.de/sneak/sfdupes/issues/132)
+  `builder`, now come before `ARG CACHEBUST`. Docker keeps them between builds.
  Every step that lints, tests or compiles still comes after it.
  `golangci-lint run` also keeps golangci-lint's cache. README says the same
  (2026-10-18, https://git.eeqj.de/sneak/sfdupes/issues/109)
- `REPO_POLICIES.md` and the four scripts that pass `CACHEBUST` were copied
+- Release rule set: until 1.0, each tip of `main` that passes the build gets the
-  again from `sneak/prompts` `next` at `0653579`. Two steps now come before
+  next `v0.0.N` tag, so `go install sneak.berlin/go/sfdupes@latest` installs it.
-  `ARG CACHEBUST`:
+  `go.mod` retracts `v0.0.1`, the early build without a database. When the
-    - the module download in the `lint`, `test` and `builder` stages of the
+  linker set no version, `sfdupes --version` prints the version Go recorded in
-      `Dockerfile`;
+  the binary: the tag, or the pseudo-version of a `go install` build. It prints
-    - the package install in `builder`.
+  `dev` only when neither is known. README "Install" documented the rule, what
-
+  `@main` and `v0.0.1` give, and how to check an installed binary (2026-10-17,
-    Docker keeps them until one of these changes:
+  https://git.eeqj.de/sneak/sfdupes/issues/116)
    - the base image;
    - the install line;
    - `go.mod` or `go.sum`.
    Every step that checks or compiles the code still comes after
    `ARG CACHEBUST`. `golangci-lint run` also keeps the linter's own cache.
    README says the same (2026-10-18,
    https://git.eeqj.de/sneak/sfdupes/issues/109)
 - The release rule was set. Until 1.0, each tip of `main` that passes the build
  gets the next `v0.0.N` tag. `go install sneak.berlin/go/sfdupes@latest` then
  installs it. `go.mod` retracts `v0.0.1`, the early build without a database.
  When the linker set no version, `sfdupes --version` prints the version Go
  recorded in the binary. That is the tag, or the pseudo-version of a
  `go install` build. It prints `dev` only when neither is known. README
  "Install" documented:
    - the rule;
    - what `@main` and `v0.0.1` give;
    - how to check an installed binary.
    (2026-10-17, https://git.eeqj.de/sneak/sfdupes/issues/116)
 - `scan` creates the database's directory where the database path leads. The
-  directory is the path with its last element cut off as text, so a `..` in it
+  directory is the path with its last element cut off as text, never cleaned. A
-  stays. A `..` after a symlinked directory therefore goes through the symlink,
+  `..` after a symlinked directory therefore goes through the symlink, as it
-  as it does when the file is opened. With
+  does when the file is opened. With
  `SFDUPES_DATABASE=/srv/link/../new/db.sqlite` and `/srv/link` a symlink to
  `/data/x`, it now creates `/data/new` and the database in it. It used to
  create `/srv/new` and then fail (2026-10-17,
  https://git.eeqj.de/sneak/sfdupes/issues/119)
 - `scan` never records its own database. Once the database and its `.lock` file
-  are open, it notes the device and inode of each of these:
+  are open, it notes the device and inode of the database file, its `-wal` and
-    - the database file;
+  `-shm` files and the `.lock` file. The walk passes over a file with one of
-    - its `-wal` and `-shm` files;
+  them wherever it reaches it, through a symlinked directory included, printing
-    - the `.lock` file.
+  no line and counting nothing. A record an earlier scan left for one of them is
  deleted (2026-10-17, https://git.eeqj.de/sneak/sfdupes/issues/115)
-    The walk passes over any file with the device and inode of one of them,
+- `scan` never records or reads anything on a filesystem that is not persistent:
-    however it reaches the file. It prints no line for such a file and counts
+  `tmpfs`, `proc`, `sysfs` and the other kernel or memory-backed types. It
-    nothing. A record an earlier scan left for one of them is deleted
+  matches them by device ID, listed as the scan starts from
-    (2026-10-17, https://git.eeqj.de/sneak/sfdupes/issues/115)
+  `/proc/self/mountinfo` on Linux and from the mount list on macOS. No flag
  turns that off. Below an operand, the walk does not enter the default excludes
  either, so `sfdupes scan /` skips the kernel's view of the running system and
  the temporary directories. On Linux those are `/proc`, `/sys`, `/dev`, `/run`,
  `/tmp` and `/var/tmp`. On macOS they are `/dev`, `/private/tmp`,
  `/private/var/tmp`, `/private/var/vm`, `/System/Volumes/VM` and
  `/System/Volumes/Data`. A Windows list exists in the code but is not used. An
  operand at or inside a default exclude is still walked. The scan prints a line
  for each path it leaves out, without counting it as skipped, and the records
  there count as outside the scanned operands, as for `-x`.
  `--no-default-excludes` turns off the default excludes only, and `scan --help`
  lists them (2026-10-17, https://git.eeqj.de/sneak/sfdupes/issues/124)
- `scan` never records or reads anything on a filesystem that is not persistent,
+- The rate a progress display shows covers the items completed over the last 5
-  such as `tmpfs` or `proc`. Such a filesystem is one the kernel makes up or
+  seconds, or since the line before when stderr is not a terminal. It falls to 0
-  keeps in memory. `scan` matches them by device ID, however the walk or the
+  while nothing completes, and a burst after a wait no longer reads as a steady
-  content phase reaches a path. As the scan starts, it lists the mounted
+  rate. The time remaining still comes from the phase's average. Once no item
-  filesystems of those types, from `/proc/self/mountinfo` on Linux and from the
+  has completed for 10 seconds, the word `stalled` and where the phase waits
-  mount list on macOS. No flag turns that off. Below an operand, the walk does
+  take the rate's place, as `stalled disk/db`. The places are `disk`, `db`,
-  not enter the default excludes either. So `sfdupes scan /` skips the kernel's
+  `out` for stdout and `cpu`, or two of them for a phase that may wait on
-  view of the running system and the temporary directories. On Linux those are:
+  either. A line too wide for the terminal loses its bar first, then its rate or
-
+  those words, so the phase, progress, elapsed time and time remaining stay
-    ```
+  whole. The content phase's last partial batch is written under a display of
-    /proc, /sys, /dev, /run, /tmp, /var/tmp
+  its own (2026-10-16, https://git.eeqj.de/sneak/sfdupes/issues/125)
    ```
    On macOS they are:
    ```
    /dev, /private/tmp, /private/var/tmp, /private/var/vm
    /System/Volumes/VM, /System/Volumes/Data
    ```
    A Windows list exists in the code but is not used. An operand at or inside a
    default exclude is still walked. The scan prints a line for each path it
    leaves out, without counting it as skipped. The records there count as
    outside the scanned operands, as for `-x`. `--no-default-excludes` turns off
    the default excludes only, and `scan --help` lists them (2026-10-17,
    https://git.eeqj.de/sneak/sfdupes/issues/124)
 - A progress display's rate covers the items completed over the last 5 seconds.
  When stderr is not a terminal, it covers the items since the line before. It
  falls to 0 while nothing completes. A burst after a wait no longer reads as a
  steady rate of over 1,000 files a second. The time remaining still comes from
  the phase's average. Once no item has completed for 10 seconds, the line shows
  `stalled` and where the phase waits in place of the rate, as
  `stalled disk/db`. The places are:
    - `disk`;
    - `db`;
    - `out`, for stdout;
    - `cpu`.
    A phase that may wait in two places names both. Each phase's word is set in
    the code that defines the phase. A line too wide for the terminal loses its
    bar first, then its rate or those words. Four parts stay whole:
    - the phase;
    - the progress;
    - the elapsed time;
    - the ETA, the time remaining.
    The content phase had one display for its checks and one for its reads. Both
    lost those words on an 80-column terminal, at counts like those of README's
    example. That happened for most elapsed times and ETAs in minutes. Every
    other phase kept them whenever the elapsed time and the ETA were both in
    minutes. The content phase writes its last partial batch, the records not
    yet written, under a display of its own (2026-10-16,
    https://git.eeqj.de/sneak/sfdupes/issues/125)
 - New subcommand `info` prints the database's details on stdout, one per line as
-  a name, a tab and the value:
+  a name, a tab and the value (2026-10-16,
  https://git.eeqj.de/sneak/sfdupes/issues/117):
    - the path and where it came from;
    - the sizes of the database file and of its `-wal` file, when there is one;
    - when the database file was last changed;
-    - the schema version;
+    - the schema version, the record counts and the sizes of all records added
-    - the number of records;
+      up.
    - how many records have `head` and `tail` hashes;
    - how many records have a content hash;
    - the sizes of all records added up.
    It opens the database as `report` does and shows two phases on stderr,
    `[1/2] open` and `[2/2] count`. The schema version and the counts come from
-    one read-only transaction, a read of the database at one moment. The counts
+    one read-only transaction, the counts from one query.
    come from one query (2026-10-16,
    https://git.eeqj.de/sneak/sfdupes/issues/117)
 - `report` shows its work on stderr in two phases, `[1/2] open` and
  `[2/2] read`, with the progress display `scan` and `trees` use. The display
@@ -223,96 +145,83 @@ are known.
  opening the database, also while it waits on a busy one. `read` counts the
  records, then reads them against that count in signature order. SQLite takes
  that order from the `files_signature` index without sorting, so the first
-  record comes at once. `report` forms the duplicate groups itself and holds
+  record comes at once. `report` forms the duplicate groups itself, holding only
-  only those of the size it is reading. It writes them ordered by first path
+  those of the size it is reading, and writes them ordered by first path before
-  before it reads the next size. stdout and the summary line are unchanged, and
+  it reads the next size. stdout and the summary line are unchanged, and SQLite
-  SQLite no longer needs a temporary file to sort in (2026-10-16,
+  no longer needs a temporary file to sort in (2026-10-16,
  https://git.eeqj.de/sneak/sfdupes/issues/114)
- `trees` shows its work on stderr in four phases, from `[1/4] open` to
+- `trees` shows its work on stderr in four phases, `[1/4] open`, `[2/4] read`,
-  `[4/4] write`, each with the progress display `scan` uses. The display runs
+  `[3/4] group` and `[4/4] write`, each with the progress display `scan` uses.
-  from the moment `trees` starts until the summary line. `open` says it is
+  The display runs from the moment `trees` starts until the summary line. `open`
-  opening the database, also while it waits on a busy one. `read` counts the
+  says it is opening the database, also while it waits on a busy one. `read`
-  records, then reads them against that count. `group` counts the directories it
+  counts the records, then reads them against that count. `group` counts the
-  groups, and `write` the groups it writes. A display's rate names what its
+  directories it groups, and `write` the groups it writes. A display's rate
-  phase counts:
+  names what its phase counts: files, records, directories or groups. stdout and
-    - files;
+  the summary line are unchanged. When stdout and stderr are the same file, as
-    - records;
+  one terminal is, no line of stdout shares a line with the display. When they
-    - directories;
+  are not, the display keeps being drawn while stdout waits on a slow reader
-    - groups.
+  (2026-10-16, https://git.eeqj.de/sneak/sfdupes/issues/113)
    stdout and the summary line are unchanged. When stdout and stderr are the
    same file, as one terminal is, no line of stdout shares a line with the
    display. When they are not, the display keeps being drawn while stdout waits
    on a slow reader (2026-10-16, https://git.eeqj.de/sneak/sfdupes/issues/113)
 - Each `scan` phase's progress display names the phase and its place among the
-  five, as `[2/5] walk`. It runs from the moment that the phase starts. It
+  five, as `[2/5] walk`, from the moment it starts, with its progress, elapsed
-  shows:
+  time and ETA. `load` counts the records first. The walk's total is estimated
-    - the progress;
+  from the records under the operands. The content phase counts the records it
-    - the elapsed time;
+  checks from SQLite's grouping alone, then says it is searching the database
-    - the ETA, the time remaining.
+  until the first one is returned. On a terminal a phase with an exact total
-
+  draws its line followed by the library's bar, and any other a spinner followed
-    `load` counts the records first. The walk's total is estimated from the
+  by the line. Every display is drawn again several times a second. No line
-    records under the operands. The content phase takes its total from SQLite's
+  reaches the terminal's last column, however narrow, also after the terminal is
-    grouping alone. Until the first record is returned, it says it is searching
+  made narrower during a phase. A line too wide leaves out its rate, then its
-    the database. On a terminal a phase with an exact total draws its line
+  bar, keeping the phase, progress, elapsed time and ETA whole. It is cut short
-    followed by the bar of the progress-bar library. Any other phase draws a
+  only when those alone do not fit, as below about 70 columns late in a large
-    spinner followed by the line. Every display is drawn again several times a
+  scan. In plain mode the line is printed every 5 seconds whether or not an item
-    second. No line reaches the terminal's last column, however narrow the
+  completed (2026-10-16, https://git.eeqj.de/sneak/sfdupes/issues/112)
    terminal is, even after it is made narrower during a phase. A line too wide
    leaves out its rate, then its bar. The rest stays whole. The line is cut
    short only when the rest alone does not fit, as below about 70 columns late
    in a large scan. When stderr is not a terminal, the line is printed every 5
    seconds whether or not an item completed (2026-10-16,
    https://git.eeqj.de/sneak/sfdupes/issues/112)
 - `scan`, `report` and `trees` first print a line on stderr naming the database
-  they use, as an absolute path. The line says whether that path is the default
+  they use, as an absolute path, and whether that path is the default or comes
-  or comes from `SFDUPES_DATABASE`. `scan` says when the database is new. README
+  from `SFDUPES_DATABASE`. `scan` says when the database is new. README
  "Database" says when `scan` writes each file (2026-10-16,
  https://git.eeqj.de/sneak/sfdupes/issues/111)
- The canonical files and model scripts were copied again from `sneak/prompts`
+- The canonical files and model scripts re-vendored from `sneak/prompts` `next`
-  `next` at `e3f79c4`:
+  at `e3f79c4` (2026-10-15, https://git.eeqj.de/sneak/sfdupes/issues/95):
-    - `golangci-lint` v2.14.0;
+    - golangci-lint v2.14.0;
    - lint and test are phases of the `Dockerfile` that write no image, and
-      `make test` runs the suite under the race detector. Gone are
+      `make test` runs the suite under the race detector. `Dockerfile.lint`,
-      `Dockerfile.lint`, `script/verify-lint-image-pin` and `make test-race`;
+      `script/verify-lint-image-pin` and `make test-race` are gone;
-    - every `docker build` in `script/` passes a new `CACHEBUST` value. Every
+    - every `docker build` in `script/` passes a new `CACHEBUST` value, which
-      stage of the `Dockerfile` declares it first, so every `RUN` step runs on
+      every stage of the `Dockerfile` declares first, so every `RUN` step runs
-      every build. The steps that compile keep Go's build cache, and the tests
+      on every build. The steps that compile keep Go's build cache, and the
-      run with `-count=1`;
+      tests run with `-count=1`;
-    - `prettier` runs on the host, from the `node` and `yarn` that
+    - prettier runs on the host, from the node and yarn `script/bootstrap`
-      `script/bootstrap` installs. The `prettier` and `markdown` stages are
+      installs, so the `prettier` and `markdown` stages are gone and the build
-      gone, and the build stage installs `git` and `make` itself;
+      stage installs `git` and `make` itself;
    - a new push cancels the workflow's older run on the same branch, and a run
      stops after 20 minutes;
-    - a coding agent's settings file is deleted.
+    - `.claude/settings.json` is deleted.
-    Since https://git.eeqj.de/sneak/sfdupes/issues/109 two steps come before
+    Since https://git.eeqj.de/sneak/sfdupes/issues/109 the module download in
-    `ARG CACHEBUST`:
+    `lint`, `test` and the build stage, and the install of `git` and `make` in
-    - the module download in `lint`, `test` and the build stage;
+    the build stage, come before `ARG CACHEBUST`. Docker keeps them between
-    - the install of `git` and `make` in the build stage.
+    builds, and every step that lints, tests or compiles still runs on every
    build.
-    Docker keeps them between builds. Every step that checks or compiles the
+- With `-x`, an operand under another operand is no longer dropped when the
-    code still runs on every build (2026-10-15,
+  outer operand's walk cannot reach it. That is the case when a directory from
-    https://git.eeqj.de/sneak/sfdupes/issues/95)
+  the inner operand up to, but not including, the outer one is on a different
 - With `-x`, an operand under another operand is no longer dropped when a
  directory between the two, the inner one included, is on a different
  filesystem than the outer one. The inner operand is then walked on its own.
-  For a regular-file operand the check starts at its directory. The records of
+  For a regular-file operand the directories checked start at its directory. The
-  files gone from below it are deleted (2026-10-14,
+  records of files gone from below it are deleted (2026-10-14,
  https://git.eeqj.de/sneak/sfdupes/issues/106)
 - With `-x`, `scan` keeps the records below a directory on another filesystem
-  under its operand, instead of deleting them. It counts their sizes in the size
+  under its operand, and counts their sizes in the size census, instead of
-  census (2026-10-14, https://git.eeqj.de/sneak/sfdupes/issues/99)
+  deleting them (2026-10-14, https://git.eeqj.de/sneak/sfdupes/issues/99)
 - The hash and content phases open each file without blocking and check that it
-  is still a regular file. A file that is now a FIFO or device node is warned
+  is still a regular file. A file replaced by a FIFO or device node after it was
-  about and skipped instead of hanging the scan (2026-10-14,
+  statted is warned about and skipped instead of hanging the scan (2026-10-14,
  https://git.eeqj.de/sneak/sfdupes/issues/100)
 - The scan lock file is named from the database's path with symlinks resolved,
@@ -338,34 +247,29 @@ are known.
 - `make test-race` ran the test suite under the race detector in a cgo-enabled
  container, outside `make check`. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 `make test` itself runs the suite
-  under the race detector, in the `Dockerfile`'s Debian-based `test` phase.
+  under the race detector, in the `Dockerfile`'s Debian-based `test` phase, and
  `make test-race` is gone (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/18)
 - A bare `docker build .` failed, naming `script/cibuild` and `script/docker`,
-  rather than serve the gates, the lint and test steps, from cache. Since
+  rather than serve the gates from cache. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 a bare build succeeds, as
  `REPO_POLICIES.md` requires, and may serve the gates from cache. The builds in
  `script/` pass a new `CACHEBUST` value, so theirs always run (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/39)
- `make fmt` and `make fmt-check` run `prettier` over all Markdown, and the
+- `make fmt` and `make fmt-check` run prettier over all Markdown, and CI checks
-  Gitea workflow checks it. All Markdown was reformatted (2026-10-04,
+  it. All Markdown was reformatted (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/19)
 - `script/lint` writes no image, so a run no longer leaves an untagged one
  behind (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/48)
- Tests cover:
+- Tests cover a missing database, `scan` keeping stdout empty, its skip warning,
-    - a missing database;
+  the `report` and `trees` summary lines, and every subcommand going through
-    - `scan` keeping stdout empty;
+  `runE` (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/16)
    - its skip warning;
    - the `report` and `trees` summary lines;
    - every subcommand going through `runE`.
-    (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/16)
+- `.golangci.yml` replaced with the current canonical copy, which uses
 - `.golangci.yml` was replaced with the current canonical copy, which uses
  `gomodguard_v2`, so lint no longer prints a deprecation warning (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/26)
@@ -384,8 +288,8 @@ are known.
 - A test checks that `scan` refuses a database with another schema version
  (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/64)
- Four inaccurate comments in `cancel_test.go` were corrected, and
+- Four inaccurate comments in `cancel_test.go` corrected, and
-  `walkCancelInFlightDirs` was renamed to `walkCancelInFlightFiles` (2026-10-04,
+  `walkCancelInFlightDirs` renamed to `walkCancelInFlightFiles` (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/33)
 - The `-x` filesystem-boundary rules in `subdirJob` are tested (2026-10-04,
@@ -395,13 +299,13 @@ are known.
  `files` table is refused with a clear schema-version error (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/11)
- README documents install, Docker, a daily `cron` scan and how to read and
+- README documents install, Docker, a daily cron scan and how to read and check
-  check the reports (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/54)
+  the reports (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/54)
 - The `Dockerfile` build stage kept the Go module cache out of `builder`'s home
  and copied the sources with `--chown`, so no `chown -R` walked them. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 there is no `builder` user and
-  nothing changes owner. The build stage only compiles, as root, and the tests
+  nothing changes owner: the build stage only compiles, as root, and the tests
  run as `nobody` in the `test` phase (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/43)
@@ -416,321 +320,234 @@ are known.
  The schema gains the `files_signature` index (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/14)
- Progress prints at once on a non-terminal and uses a real terminal test.
+- Progress prints at once on a non-terminal, uses a real terminal test, and
-  Warnings print through a spinner instead of racing its redraw (2026-10-03,
+  prints warnings through a spinner instead of racing its redraw (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/13)
- These operands are warned about and skipped, and the records beneath them are
+- Symlink, socket, FIFO, device and `.zfs` operands are warned about and
-  kept:
+  skipped, and the records beneath them are kept (2026-10-03,
-    - symlinks;
+  https://git.eeqj.de/sneak/sfdupes/issues/9)
    - sockets;
    - FIFOs;
    - device nodes;
    - `.zfs` directories.
    (2026-10-03, https://git.eeqj.de/sneak/sfdupes/issues/9)
 - `scan` holds a lock on a lock file beside the database for its whole run, so a
  second `scan` fails at once with exit 1 (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/53)
 - Tests cover stdout write failures in `report` and `trees`. README states that
-  `| head` ends `sfdupes` by `SIGPIPE` and that `>&-` writes to `/dev/null`
+  `| head` ends sfdupes by `SIGPIPE` and that `>&-` writes to `/dev/null`
  (2026-10-03, https://git.eeqj.de/sneak/sfdupes/issues/30)
 - `report` and `trees` open the database read-only, and `scan` leaves it out of
  WAL mode, so reading needs only read access (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/8)
- Four characters are escaped in `report`, `trees` and warning paths:
+- Tabs, newlines, carriage returns and backslashes are escaped in report, trees
-    - tab;
+  and warning paths. The root directory's path is `/` (2026-10-03,
-    - newline;
+  https://git.eeqj.de/sneak/sfdupes/issues/7)
    - carriage return;
    - backslash.
-    The root directory's path is `/` (2026-10-03,
+- A plain `docker build .` stamps the git tag or short commit instead of `dev`.
-    https://git.eeqj.de/sneak/sfdupes/issues/7)
+  `.dockerignore` sends `.git` without `.git/config`. The build stage stamps the
-
+  `VERSION` build argument, else `git describe --tags --always`. It fails if the
- A plain `docker build .` stamps the `git` tag or short commit instead of
+  context carries `.git` and the version is still empty, `dev` or `unknown`. CI
-  `dev`. `.dockerignore` sends `.git` without `.git/config`. The build stage
+  checks out the full history (`fetch-depth: 0`), so it stamps the same value as
-  stamps the `VERSION` build argument, else `git describe --tags --always`. It
+  `make build` (2026-10-02, branch `next`,
  fails if the context carries `.git` and the version is still empty, `dev` or
  `unknown`. The Gitea workflow checks out the full history (`fetch-depth: 0`),
  so it stamps the same value as `make build` (2026-10-02, branch `next`,
  https://git.eeqj.de/sneak/sfdupes/issues/67)
- The 1 KiB end-window sampling was replaced with the hashes chosen by file
+- The 1 KiB end-window sampling was replaced with the head/tail plus
-  size, and README "Duplicate detection" documented every size threshold. A file
+  content-hash ladder, and README "Duplicate detection" documented every rung. A
-  under 10 MiB was hashed in full, and its `head`, `tail` and `content` all held
+  file under 10 MiB was hashed in full, and its `head`, `tail` and `content` all
-  that hash. A larger file got only its 64 KiB `head` and `tail` in the hash
+  held that hash. A larger file got only its 64 KiB `head` and `tail` in the
-  phase. The content phase ran after the update phase. It read a file for
+  hash phase. The content phase, after the update phase, read it for `content`
-  `content` only when its size, `head` and `tail` matched another record's, from
+  only when its size, `head` and `tail` matched another record's. `content` was
-  this scan or an earlier one. `content` was the whole file below 50 MiB, and
+  the whole file below 50 MiB, and gigabyte-spaced 1 MiB samples at or above. A
-  gigabyte-spaced 1 MiB samples at or above. It never read a file gone or
+  file gone or changed since its record was written was never read. `report` and
-  changed since its record was written. `report` and `trees` left out any record
+  `trees` left out any record without a `content` hash. The `content` column is
-  without a `content` hash. The `content` column is part of the version 1
+  part of the version 1 schema. Superseded by
-  schema. Superseded by https://git.eeqj.de/sneak/sfdupes/issues/132
+  https://git.eeqj.de/sneak/sfdupes/issues/132 (2026-09-22, branch `next`,
-  (2026-09-22, branch `next`, https://git.eeqj.de/sneak/sfdupes/issues/61)
+  https://git.eeqj.de/sneak/sfdupes/issues/61)
- The dead `files.dat` references were removed from `Makefile`, `.gitignore` and
+- The dead `files.dat` references removed from `Makefile`, `.gitignore` and
  `.dockerignore` (2026-09-21, branch `next`,
  https://git.eeqj.de/sneak/sfdupes/issues/22)
 - The lint-image pin comments and `FROM` form in `Dockerfile` and
-  `Dockerfile.lint` were fixed. Both pins became the policy
+  `Dockerfile.lint` fixed. Both pins became the policy
  `# image:vX.Y.Z, YYYY-MM-DD` comment over a bare `FROM image@sha256:...`,
  without the false `(Debian-based)` note or the tag. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 the `Dockerfile`'s `lint` phase
-  holds the only `golangci-lint` pin, in that form. `Dockerfile.lint` is gone,
+  holds the only golangci-lint pin, in that form. `Dockerfile.lint` and
-  and so is `script/verify-lint-image-pin`, which compared the two pins
+  `script/verify-lint-image-pin`, which compared the two pins, are gone
  (2026-08-10, branch `next`, https://git.eeqj.de/sneak/sfdupes/issues/25)
- All linting ran in Docker, via `Dockerfile.lint` and `script/lint`. Per the
+- All linting runs in Docker, via `Dockerfile.lint` and `script/lint`. Per the
  owner ruling the linter is never installed on a host, and
  `golangci-lint config verify` runs before `golangci-lint run`.
  `script/bootstrap` stopped installing or pinning the linter, and
  `script/verify-linter-pin` was retired. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 both commands run in the
-  `Dockerfile`'s `lint` phase. `script/lint` builds that phase alone, and the
+  `Dockerfile`'s `lint` phase, which `script/lint` builds alone and the build
-  build stage depends on it through `COPY --from=lint /src/go.sum /dev/null`.
+  stage depends on through `COPY --from=lint /src/go.sum /dev/null`.
  `Dockerfile.lint` and `script/verify-lint-image-pin` are gone. Nothing inside
-  an image build may run `docker`, so the phase calls `golangci-lint` directly
+  an image build may run docker, so the phase calls `golangci-lint` directly
  (2026-08-10, branch `next`, https://git.eeqj.de/sneak/sfdupes/issues/46)
 - The Docker build stage's prerequisites were installed by running
  `script/bootstrap` instead of `apk add --no-cache make` inline.
  `script/verify-linter-pin` failed the build unless the linter copied from the
-  lint stage was the version that `script/bootstrap` pinned. Builds then took up
+  lint stage was the version `script/bootstrap` pinned. Builds then took up to
-  to 5m14s from an empty cache, mostly in a `chown -R` of the module cache,
+  5m14s cold, mostly in a `chown -R` of the module cache, filed as
-  filed as https://git.eeqj.de/sneak/sfdupes/issues/43. Since
+  https://git.eeqj.de/sneak/sfdupes/issues/43. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 the build stage installs `git` and
-  `make` with `apk add --no-cache` and only compiles. The `lint` and `test`
+  `make` with `apk add --no-cache` and only compiles; the `lint` and `test`
  phases are the gates (2026-08-09, branch `dockerfile-bootstrap`,
  https://git.eeqj.de/sneak/sfdupes/issues/42)
- The Docker layer cache is defeated for the gate steps, so `script/cibuild` and
+- The Docker layer cache is busted for the gate steps, so `script/cibuild` and
-  `script/docker` cannot report a pass they did not earn. The `Dockerfile`
+  `script/docker` cannot report a green they did not earn. The `Dockerfile`
-  copies the tree before its gates. On an unchanged tree Docker served them from
+  copies the tree before its gates, so on an unchanged tree Docker served them
-  cache, and the build exited 0 without running them. The fix was a
+  from cache and the build exited 0 having run nothing. The fix was a
  `CHECK_EPOCH` build argument. Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 every `docker build` in `script/`
-  passes a new `CACHEBUST` value instead. Every stage of the `Dockerfile`
+  passes a new `CACHEBUST` value instead, which every stage of the `Dockerfile`
-  declares it before every step that checks or compiles the code. Run as root,
+  declares before every step that lints, tests or compiles. Run as root, the
-  the tests fail `TestScanHardlinkRunFailsTogether`, because root reads through
+  tests fail `TestScanHardlinkRunFailsTogether`, because root reads through the
-  the `chmod(0)` the test relies on. So the `test` phase runs them as `nobody`
+  `chmod(0)` the test relies on, so the `test` phase runs them as `nobody`
  (2026-08-09, branch `cibuild-cache-bust`,
  https://git.eeqj.de/sneak/sfdupes/issues/32)
- `script/bootstrap` checked the installed `golangci-lint` version instead of
+- `script/bootstrap` checked the installed golangci-lint version instead of only
-  only its presence. The version lived only in `GOLANGCI_LINT_VERSION`, with the
+  its presence. The version lived only in `GOLANGCI_LINT_VERSION`, with the
-  `go install` module reference derived from it. Any installed version that was
+  `go install` module ref derived from it, and any installed version that was
-  not the pin was reinstalled, whether:
+  not the pin was reinstalled. `go install` writes into `GOBIN` (or
-    - older;
+  `GOPATH/bin`) while `make lint` ran the first `golangci-lint` on `PATH`, so
-    - newer;
+  bootstrap re-read the effective version after installing. On a mismatch it
-    - absent;
+  printed both paths and both versions and exited non-zero; it did not reorder
-    - unparseable.
+  `PATH` or delete anyone's binary. The `--version` call kept its stderr and was
-
+  bounded by `timeout(1)` where that exists. `git`, `make` and `go` kept
-    `go install` writes into `GOBIN`, or `GOPATH/bin`, while `make lint` ran the
+  presence-only checks. Superseded by
-    first `golangci-lint` on `PATH`. So bootstrap re-read the effective version
+  https://git.eeqj.de/sneak/sfdupes/issues/46: the linter is no longer installed
-    after installing. On a mismatch it printed both paths and both versions and
+  on a host (2026-08-09, branch `bootstrap-version-check`,
-    exited non-zero. It did not reorder `PATH` or delete anyone's binary. The
+  https://git.eeqj.de/sneak/sfdupes/issues/24)
    `--version` call kept its stderr and was bounded by `timeout(1)` where that
    exists. `git`, `make` and `go` kept presence-only checks. The version check
    was verified by bootstrapping this host from v2.10.1 to v2.12.2, and again
    to a no-op. Stub runs of the script under `dash` covered:
    - a thirteen-input version-parse matrix;
    - a shadowed install, which must exit non-zero;
    - an install destination not on `PATH`;
    - `GOBIN` set;
    - a wedged binary, which must hit the timeout.
    `make check` and `make lint` were clean at v2.12.2, so v2.10.1 had not been
    hiding findings on `main`. Superseded by
    https://git.eeqj.de/sneak/sfdupes/issues/46, since the linter is no longer
    installed on a host (2026-08-09, branch `bootstrap-version-check`,
    https://git.eeqj.de/sneak/sfdupes/issues/24)
 - The hash worker pool unwinds on the error path. The pool is an owned,
  context-aware `hashPool`. Every blocking send in the feeder and the workers
  selects on `ctx.Done()`, and `jobs` is closed on every path out. `hashPhase`
  defers `pool.stop()`, which cancels and then drains `results` until the last
-  goroutine has exited. Draining is what frees a worker parked on a send. `ctx`
+  goroutine has exited; draining is what frees a worker parked on a send. `ctx`
-  is passed from `cmd.Context()` as the first parameter, through:
+  is threaded from `cmd.Context()` through `runScan`, `syncScan`, both worker
-    - `runScan`;
+  pools and the whole database layer, as the first parameter everywhere. The
-    - `syncScan`;
+  walk pool gets the same treatment, plus a `ctx.Err()` guard after the walk. A
-    - both worker pools;
+  cancelled walk yields a partial size census, and every file it never reached
-    - the whole database layer.
+  looks vanished to the update phase. The guard is the barrier that still holds
-
+  once an interrupted scan may commit what it has. Tests drive `run(scan)`
-    The walk pool gets the same treatment, plus a `ctx.Err()` guard after the
+  against a database whose insert trigger aborts, and assert that the scan fails
-    walk. A cancelled walk yields a partial size census, and every file that it
+  instead of hanging and that the goroutine count returns to its pre-scan
-    never reached looks vanished to the update phase. That phase's own `BeginTx`
+  baseline. Other tests cancel a scan part-way through the walk and assert that
-    also fails on the cancelled context before deleting anything. The guard is
+  it stops at the guard with every record intact (2026-08-09, branch
-    still the barrier once an interrupted scan may commit what it has. Tests
+  `hash-pool-cleanup`, https://git.eeqj.de/sneak/sfdupes/issues/6)
    drive `run(scan)` against a database whose insert trigger aborts. They
    assert that the scan fails instead of hanging, and that the goroutine count
    returns to its pre-scan baseline. Other tests cancel a scan part-way through
    the walk, deterministically, by counting the scan's own checks of
    `ctx.Done()`. They assert that it stops at the guard with every record
    intact. It then holds a partial size census and a still-populated record
    index. Direct tests cover the remaining cancellation branches of both pools.
    They test:
    - `sendEvent`;
    - the walk workers;
    - `dispatchDirs`;
    - `feedHashJobs`;
    - `hashWorker`;
    - `hashPhase`.
    (2026-08-09, branch `hash-pool-cleanup`,
    https://git.eeqj.de/sneak/sfdupes/issues/6)
 - The database is closed on every fatal exit path. `fatalf` and its `os.Exit(1)`
-  are gone. So the deferred `db.Close()` runs when a subcommand fails, and with
+  are gone, so the deferred `db.Close()`, and with it the SQLite WAL checkpoint,
-  it the SQLite WAL checkpoint. These return errors instead:
+  runs when a subcommand fails. `runScan`, `runReport`, `runTrees`,
-    - `runScan`;
+  `loadRecords` and `resolveRoots` return errors instead. The single exit point
-    - `runReport`;
+  is `run` in `main.go`. It maps a `fatalError` to exit 1 and cobra's own
-    - `runTrees`;
+  argument and flag errors to exit 2, so a runtime failure is never reported as
-    - `loadRecords`;
+  a usage error. `main_test.go` drives the CLI in-process and asserts the exit
-    - `resolveRoots`.
+  codes from README "Error handling" and the stdout/stderr split. That includes
  a fatal error after the database is open leaving no `-wal` or `-shm` file
  behind (2026-08-09, branch `db-close-on-fatal`,
  https://git.eeqj.de/sneak/sfdupes/issues/4)
-    The single exit point is `run` in `main.go`. It maps a `fatalError`,
+- golangci-lint updated to v2.12.2 with the canonical config, merged as
    anything a subcommand returned, to exit 1, and cobra's own argument and flag
    errors to exit 2. So a runtime failure is never reported as a usage error,
    nor printed with the usage text. `main_test.go` drives the CLI in-process
    and asserts the exit codes from README "Error handling" and the
    stdout/stderr split. It also checks that a fatal error after the database is
    open leaves no `-wal` or `-shm` file behind, for `scan`, `report` or `trees`
    (2026-08-09, branch `db-close-on-fatal`,
    https://git.eeqj.de/sneak/sfdupes/issues/4)
 - `golangci-lint` was updated to v2.12.2 with the canonical config, merged as
  `38a01bd`. The pinned linter in the `Dockerfile` lint stage and
  `script/bootstrap` went from v2.12.1 to v2.12.2, and `.golangci.yml` was
-  replaced with the canonical file. Four thresholds now live under
+  replaced with the canonical file. The linter settings (`lll`, `funlen`,
-  `linters.settings`, as the v2 schema requires, so they are applied:
+  `cyclop`, `dupl` thresholds) now live under `linters.settings`, per the v2
-    - `lll`;
+  schema, so they are applied. No new lint findings surfaced (2026-08-09, branch
-    - `funlen`;
+  `golangci-v2.12.2`, https://git.eeqj.de/sneak/sfdupes/issues/3)
    - `cyclop`;
    - `dupl`.
-    No new lint findings surfaced (2026-08-09, branch `golangci-v2.12.2`,
+- Makefile targets converted to scripts-to-rule-them-all `script/` entrypoints,
-    https://git.eeqj.de/sneak/sfdupes/issues/3)
+  like the other managed repos. All 12 entrypoints exist, and every Makefile
  target is a thin shim over them (2026-07-26, commit `3abeacf`,
  https://git.eeqj.de/sneak/sfdupes/issues/1)
- `Makefile` targets were converted to scripts-to-rule-them-all `script/`
+- The binary is the default Make target: plain `make` builds `sfdupes`, where it
-  entrypoints, like the other managed repos. All 12 entrypoints exist:
+  used to run `check` plus `build`. `make build` remains as an alias
    - `bootstrap`, `setup` and `projectname`;
    - `test`, `lint`, `fmt`, `fmt-check` and `check`;
    - `docker`, `cibuild`, `precommit` and `install-precommit`.
    Every `Makefile` target does nothing but call its script (2026-07-26, commit
    `3abeacf`, https://git.eeqj.de/sneak/sfdupes/issues/1)
 - The binary is the default `make` target. Plain `make` builds `sfdupes`, where
  it used to run `check` plus `build`. `make build` remains as an alias
  (2026-07-24, branch `make-default-target`)
- The phases became scan-wide, with concurrent operands and batched updates. All
+- Scan-wide phases, concurrent operands and batched updates. All operands seed
-  operands seed the shared walk pool, and every pass runs once over the whole
+  the shared walk pool, and every pass runs once over the whole scan, so totals
-  scan. So the totals and ETAs cover the whole scan. The per-operand walk, hash
+  and ETAs are scan-global. The per-operand walk, hash and update cycles and
-  and update cycles and their stderr announcements are gone. The update pass
+  their stderr announcements are gone. The update pass commits in batched
-  writes in batches, each in its own transaction. The filesystem is
+  transactions. The filesystem is authoritative and the database an
-  authoritative and the database follows it, so one scan's changes need not land
+  eventually-consistent reflection of it, so scan-level atomicity is not
-  all at once (2026-07-24, branch `scan-wide-phases`)
+  required (2026-07-24, branch `scan-wide-phases`)
- The stat pass was split back out of the walk. Phases are strictly sequential
+- The stat pass split back out of the walk. Phases are strictly sequential
-  again, per operand, with parallelism only inside each phase:
+  again, walk, stat, hash and update per operand, with parallelism only inside
-    - walk;
+  each phase. The walk enumerates paths with per-directory workers, and the stat
-    - stat;
+  pass lstats them with per-file workers, restoring the exact total and ETA of
-    - hash;
+  the stat bar (2026-07-24, branch `parallel-phases`)
    - update.
    The walk enumerates paths with per-directory workers, and the stat pass
    lstats them with per-file workers. That restores the exact total and ETA of
    the stat bar (2026-07-24, branch `parallel-phases`)
 - Each operand is announced on stderr before its passes. With per-operand walk,
  hash and update cycles, a multi-operand run such as `scan /srv/*` showed pass
  totals that looked like the whole run's (2026-07-24, branch
  `scan-operand-progress`)
- The walk became parallel. The walk pass was a single goroutine and took hours
+- Parallel walk. The walk pass was a single goroutine and took hours at about 20
-  at about 20 million files on a busy pool. One ZFS server took 4 hours for 22
+  million files on a busy pool: 22 million files in 4 hours on a ZFS server. It
-  million files. It is now a walk by a pool of per-directory workers that
+  is now a per-directory worker-pool traversal that records size and mtime
-  records size and mtime as it goes. That folds away the separate stat pass and
+  during the walk, folding away the separate stat pass and halving metadata I/O.
-  halves the metadata reads. Each `PATH` operand commits in its own transaction,
+  Each `PATH` operand commits in its own transaction, so an interrupted scan
-  so an interrupted scan keeps completed operands (2026-07-24, branch
+  keeps completed operands (2026-07-24, branch `parallel-walk`)
  `parallel-walk`)
- `scan` gained a persistent database. It maintains an SQLite database that
+- Persistent scan database. `scan` maintains a SQLite database
-  survives between runs, with the absolute path as each record's key. The driver
+  (`modernc.org/sqlite`, pure Go, cgo stays disabled), keyed by absolute path,
-  is `modernc.org/sqlite`, pure Go, so cgo stays disabled. A rescan hashes only
+  that survives between runs. A rescan hashes only new or changed files, by
-  new or changed files, by mtime and size. It deletes the records of files
+  mtime and size. It deletes the records of files vanished from under the
-  vanished from under the scanned operands and leaves records outside them
+  scanned operands and leaves records outside them untouched, so `scan` can be
-  untouched. So `scan` can run daily from `cron`. `report` and `trees` read the
+  cronned daily. `report` and `trees` read the database, with no positional
-  database, with no positional arguments, instead of a scan stream. The database
+  arguments, instead of a scan stream. The database is at
-  is at `/var/lib/sfdupes/db.sqlite`, and `SFDUPES_DATABASE` overrides that. WAL
+  `/var/lib/sfdupes/db.sqlite`, overridable via `SFDUPES_DATABASE`. WAL
  journaling plus a single-transaction update keep a report run during a scan
  safe (2026-07-24, branch `persistent-database`)
- The `origin` remote, `git@git.eeqj.de:sneak/sfdupes.git`, was added. `v0.0.1`
+- The `origin` remote (`git@git.eeqj.de:sneak/sfdupes.git`) added, `v0.0.1`
-  was tagged, and `main` and the tags were pushed (2026-07-23)
+  tagged, and `main` plus tags pushed (2026-07-23)
- The `scan` command line was reworked. Required `PATH...` operands, parsed by
+- `scan` CLI rework. Required `PATH...` operands via cobra replace the `/srv`
-  cobra, replace the `/srv` `-root` default. The new `-x`, `--one-file-system`
+  `-root` default. The new `-x`/`--one-file-system` flag (GNU convention) stops
-  flag follows the GNU convention and stops at filesystem boundaries, which the
+  at filesystem boundaries, which are crossed by default (2026-07-23, branch
-  walk crosses by default (2026-07-23, branch `scan-required-paths`)
+  `scan-required-paths`)
- The repo was brought into compliance with `REPO_POLICIES.md` (the version of
+- The repo brought into compliance with `REPO_POLICIES.md` (2026-07-06), the
-  2026-07-06), the existing repo checklist and the Go styleguide. The audit of
+  existing repo checklist and the Go styleguide, audited 2026-07-22 (2026-07-23,
-  2026-07-22 found these gaps, and the branch closed them:
+  branch `repo-policy-compliance`). Added or fixed:
-    - `.gitignore`, with the standard patterns for secrets and for OS, editor
+    - `.gitignore`, with OS, editor, Go and secrets patterns; the compiled
-      and Go files. The compiled `sfdupes` binary and `files.dat` had been
+      `sfdupes` binary and `files.dat` had been sitting untracked in the tree;
      sitting untracked in the tree;
    - `.editorconfig`;
-    - `LICENSE` and the README License section. MIT was assumed from house
+    - `LICENSE` (MIT) and the README License section;
      convention, for the owner to confirm;
    - `REPO_POLICIES.md` in the repo root;
-    - the canonical `.golangci.yml`, with its 150 findings fixed, so that
+    - the canonical `.golangci.yml`, with the 150 findings it raised fixed;
-      `make lint` is clean;
+    - the `Makefile` targets `test`, `lint`, `fmt`, `fmt-check`, `docker` and
-    - the `Makefile` targets the policy requires:
+      `hooks`, and a `check` target that no longer depends on `build`;
-        - `test` and `lint`;
+    - a test suite covering parsing, grouping, digests, suppression, hashing and
-        - `fmt` and `fmt-check`;
+      the scan pipeline, at 64% coverage;
-        - `docker` and `hooks`.
+    - a multistage `Dockerfile` with hash-pinned images, and `.dockerignore`;
        `check` depended on `build`, which wrote the binary. `make check` must
        not modify files, so `check` no longer depends on `build`;
    - a test suite, which the policy required with a 30-second timeout and the
      conditional `-v` rerun. At 64% coverage, it covers:
        - parsing and grouping;
        - digests and suppression;
        - hashing and the scan pipeline;
    - a multistage `Dockerfile` and `.dockerignore`. The `Dockerfile` had:
        - hash-pinned images;
        - a lint stage that failed fast;
        - a build stage that ran `make check`;
    - `.gitea/workflows/check.yml`, running `docker build .` on push with the
      checkout action pinned by commit SHA;
-    - the README sections the policy requires. The first is a Description whose
+    - the README sections the policy requires;
      first line names the project, its purpose and category, its license and
      its author. Then come Getting Started and Rationale, and at the end TODO,
      License and Author;
    - the stale README non-goal "no git repository setup and no CI" removed;
-    - the pre-commit hook, installed with `make hooks` once that target existed.
+    - the pre-commit hook installed.
-    The code was already `gofmt`-clean, so no standalone formatting commit was
+- `git init` with a README-only first commit; the code baseline committed on
-    needed (2026-07-23, branch `repo-policy-compliance`)
+  `main` (2026-07-22)
- `git init` was run, with a README-only first commit. The code baseline was
+- `scan`, `report` and `trees` subcommands implemented (pre-git history)
  committed on `main` (2026-07-22)
 - The `scan`, `report` and `trees` subcommands were implemented (pre-git
  history)
 # Future Steps
- Possible later features, out of scope per README, are a byte-for-byte check of
+- Possible later features, out of scope per README: full-content verification of
-  candidates and helper scripts for removal.
+  candidates, and helper scripts for removal.
 # Accepted Divergences
@@ -47,15 +47,14 @@ const dbFilePerm = 0o644
 const lockFilePerm = 0o600
 // createTableSQL is the schema applied to a fresh database. Paths are
-// BLOBs because Unix paths are raw bytes, not guaranteed UTF-8.
+// BLOBs because Unix paths are raw bytes, not guaranteed UTF-8. mtime
-// disk_size holds the bytes the file takes on disk. mtime holds whole
+// holds whole Unix seconds and mtime_nsec the nanoseconds within that
-// Unix seconds and mtime_nsec the nanoseconds within that second. head,
+// second. head, tail and content each hold the raw 32 bytes of a
-// tail and content each hold the raw 32 bytes of a SHA-256.
+// SHA-256.
 const createTableSQL = `
 CREATE TABLE files (
    path       BLOB PRIMARY KEY,
    size       INTEGER NOT NULL,
    disk_size  INTEGER NOT NULL,
    mtime      INTEGER NOT NULL,
    mtime_nsec INTEGER NOT NULL,
    head       BLOB NOT NULL,
@@ -70,59 +69,14 @@ const createIndexSQL = `
 CREATE INDEX files_signature ON files (size, head, tail, content)
 `
 // createTotalsSQL creates the totals table, which holds one row: the
 // number of records and the sizes of all records added up. Counting
 // them over files would read every record. The three triggers below
 // keep the row current, in the transaction of each change to files.
 const createTotalsSQL = `
 CREATE TABLE totals (
    records INTEGER NOT NULL,
    size    INTEGER NOT NULL
 )
 `
 // insertTotalsSQL adds the one row of totals, for an empty files table.
 const insertTotalsSQL = `
 INSERT INTO totals (records, size) VALUES (0, 0)
 `
 // totalsAfterInsertSQL counts each inserted record into totals.
 const totalsAfterInsertSQL = `
 CREATE TRIGGER totals_after_insert AFTER INSERT ON files BEGIN
    UPDATE totals SET records = records + 1, size = size + NEW.size;
 END
 `
 // totalsAfterDeleteSQL takes each deleted record out of totals.
 const totalsAfterDeleteSQL = `
 CREATE TRIGGER totals_after_delete AFTER DELETE ON files BEGIN
    UPDATE totals SET records = records - 1, size = size - OLD.size;
 END
 `
 // totalsAfterUpdateSQL replaces a record's old size in totals with its
 // new one. scan's upsert of an existing record is such an update.
 const totalsAfterUpdateSQL = `
 CREATE TRIGGER totals_after_update AFTER UPDATE OF size ON files BEGIN
    UPDATE totals SET size = size + NEW.size - OLD.size;
 END
 `
 // recordCountSQL reads the number of records from totals.
 const recordCountSQL = `
 SELECT records FROM totals
 `
 // upsertSQL inserts one file record, replacing any existing record for
 // the same path.
 const upsertSQL = `
-INSERT INTO files (
+INSERT INTO files (path, size, mtime, mtime_nsec, head, tail, content)
-    path, size, disk_size, mtime, mtime_nsec, head, tail, content
+VALUES (?, ?, ?, ?, ?, ?, ?)
 )
 VALUES (?, ?, ?, ?, ?, ?, ?, ?)
 ON CONFLICT (path) DO UPDATE SET
-    size = excluded.size, disk_size = excluded.disk_size,
+    size = excluded.size, mtime = excluded.mtime,
-    mtime = excluded.mtime, mtime_nsec = excluded.mtime_nsec,
+    mtime_nsec = excluded.mtime_nsec,
    head = excluded.head, tail = excluded.tail,
    content = excluded.content
 `
@@ -196,14 +150,9 @@ func createDatabaseDirectory(path string) error {
 // scanParams are the connection parameters for scan: read-write, with
 // WAL journaling and a busy timeout, so a report can run while a cron
 // scan is in progress. closeScanDatabase leaves WAL mode again.
 //
 // Each write to files fires a trigger, so SQLite keeps a statement
 // journal for it. temp_store(MEMORY) keeps that journal in memory,
 // which costs far less than a temporary file.
 const scanParams = "_pragma=busy_timeout(10000)" +
 	"&_pragma=journal_mode(WAL)" +
-	"&_pragma=synchronous(NORMAL)" +
+	"&_pragma=synchronous(NORMAL)"
 	"&_pragma=temp_store(MEMORY)"
 // reportParams are the connection parameters for report, trees and
 // info: read-only, with the same busy timeout. They set no journal
@@ -477,14 +426,14 @@ func createSchema(ctx context.Context, db *sql.DB) error {
 	defer func() { _ = tx.Rollback() }()
-	for _, stmt := range []string{
+	_, err = tx.ExecContext(ctx, createTableSQL)
-		createTableSQL, createIndexSQL, createTotalsSQL, insertTotalsSQL,
+	if err != nil {
-		totalsAfterInsertSQL, totalsAfterDeleteSQL, totalsAfterUpdateSQL,
+		return fmt.Errorf("create schema: %w", err)
-	} {
+	}
-		_, err = tx.ExecContext(ctx, stmt)
+
-		if err != nil {
+	_, err = tx.ExecContext(ctx, createIndexSQL)
-			return fmt.Errorf("create schema: %w", err)
+	if err != nil {
-		}
+		return fmt.Errorf("create schema: %w", err)
 	}
 	_, err = tx.ExecContext(ctx,
@@ -531,7 +480,7 @@ func loadFileRows(ctx context.Context, db *sql.DB, total func(n int64),
 	var n int64
-	err = tx.QueryRowContext(ctx, recordCountSQL).Scan(&n)
+	err = tx.QueryRowContext(ctx, "SELECT COUNT(*) FROM files").Scan(&n)
 	if err != nil {
 		return fmt.Errorf("count records: %w", err)
 	}
@@ -539,8 +488,8 @@ func loadFileRows(ctx context.Context, db *sql.DB, total func(n int64),
 	total(n)
 	rows, err := tx.QueryContext(ctx,
-		"SELECT path, size, disk_size, mtime, mtime_nsec, head, tail, "+
+		"SELECT path, size, mtime, mtime_nsec, head, tail, content "+
-			"content FROM files ORDER BY path")
+			"FROM files ORDER BY path")
 	if err != nil {
 		return fmt.Errorf("read records: %w", err)
 	}
@@ -554,8 +503,7 @@ func loadFileRows(ctx context.Context, db *sql.DB, total func(n int64),
 			r                         scanRec
 		)
-		err = rows.Scan(&path, &r.size, &r.diskSize, &sec, &nsec,
+		err = rows.Scan(&path, &r.size, &sec, &nsec, &head, &tail, &content)
 			&head, &tail, &content)
 		if err != nil {
 			return fmt.Errorf("read record: %w", err)
 		}
@@ -590,11 +538,10 @@ ORDER BY size DESC, head DESC, tail DESC, content DESC
 `
 // loadSignatureRows gives total the number of records, then streams
-// every record's signature and path to fn, without its mtime or its
+// every record's signature and path to fn, without its mtime, in the
-// disk_size, in the order of signatureRowsSQL. The count and the
+// order of signatureRowsSQL. The count and the records are read in one
-// records are read in one transaction, so they agree while a scan is
+// transaction, so they agree while a scan is committing. An error from
-// committing. An error from fn stops the reading and is returned as it
+// fn stops the reading and is returned as it is.
 // is.
 func loadSignatureRows(ctx context.Context, db *sql.DB,
 	total func(n int64), fn func(r scanRec) error,
 ) error {
@@ -609,7 +556,7 @@ func loadSignatureRows(ctx context.Context, db *sql.DB,
 	var n int64
-	err = tx.QueryRowContext(ctx, recordCountSQL).Scan(&n)
+	err = tx.QueryRowContext(ctx, "SELECT COUNT(*) FROM files").Scan(&n)
 	if err != nil {
 		return fmt.Errorf("count records: %w", err)
 	}
@@ -675,7 +622,7 @@ func (r *scanRec) setHashes(head, tail, content []byte) error {
 func countRecords(ctx context.Context, db *sql.DB) (int64, error) {
 	var n int64
-	err := db.QueryRowContext(ctx, recordCountSQL).Scan(&n)
+	err := db.QueryRowContext(ctx, "SELECT COUNT(*) FROM files").Scan(&n)
 	if err != nil {
 		return 0, fmt.Errorf("count records: %w", err)
 	}
@@ -683,10 +630,12 @@ func countRecords(ctx context.Context, db *sql.DB) (int64, error) {
 	return n, nil
 }
-// databaseCountsSQL reads the number of records and the sizes of all
+// databaseCountsSQL counts the records and adds up their sizes, in one
-// records added up from totals.
+// pass over the table. A SUM over no rows is NULL, so on an empty table
 // the SUM falls back to 0.
 const databaseCountsSQL = `
-SELECT records, size FROM totals
+SELECT COUNT(*), COALESCE(SUM(size), 0)
 FROM files
 `
 // databaseCounts is what info reads from the database: its schema
@@ -729,15 +678,15 @@ func readDatabaseCounts(ctx context.Context,
 	return c, nil
 }
-// loadFileMeta streams every record's path, size, disk_size and mtime
+// loadFileMeta streams every record's path, size and mtime to fn. Scan
-// to fn. Scan change detection needs no hash values, and skipping the
+// change detection needs no hash values, and skipping the hash columns
-// hash columns keeps the scan's in-memory index small on
+// keeps the scan's in-memory index small on multi-million-file
-// multi-million-file databases.
+// databases.
 func loadFileMeta(ctx context.Context, db *sql.DB,
-	fn func(path string, m fileMeta),
+	fn func(path string, size int64, mtime time.Time),
 ) error {
 	rows, err := db.QueryContext(ctx,
-		"SELECT path, size, disk_size, mtime, mtime_nsec FROM files")
+		"SELECT path, size, mtime, mtime_nsec FROM files")
 	if err != nil {
 		return fmt.Errorf("read records: %w", err)
 	}
@@ -746,19 +695,16 @@ func loadFileMeta(ctx context.Context, db *sql.DB,
 	for rows.Next() {
 		var (
-			path      []byte
+			path            []byte
-			m         fileMeta
+			size, sec, nsec int64
 			sec, nsec int64
 		)
-		err = rows.Scan(&path, &m.size, &m.diskSize, &sec, &nsec)
+		err = rows.Scan(&path, &size, &sec, &nsec)
 		if err != nil {
 			return fmt.Errorf("read record: %w", err)
 		}
-		m.mtime = time.Unix(sec, nsec)
+		fn(string(path), size, time.Unix(sec, nsec))
 		fn(string(path), m)
 	}
 	err = rows.Err()
@@ -776,21 +722,21 @@ func loadFileMeta(ctx context.Context, db *sql.DB,
 // WAL small and let concurrent reports observe progress.
 const updateBatchSize = 10000
-// applyChanges writes upserts for new and changed files and deletes for
+// applyChanges writes one scan's database changes — upserts for new and
-// vanished ones, in batched transactions. Progress is rendered on prog
+// changed files, deletes for vanished ones — in batched transactions.
-// (one increment per change).
+// Progress is rendered on prog (one increment per change).
 func applyChanges(ctx context.Context, db *sql.DB, upserts []scanRec,
 	deletes []string, prog *progress,
 ) error {
 	for batch := range slices.Chunk(upserts, updateBatchSize) {
-		err := applyBatch(ctx, db, batch, nil, nil, prog)
+		err := applyBatch(ctx, db, batch, nil, prog)
 		if err != nil {
 			return err
 		}
 	}
 	for batch := range slices.Chunk(deletes, updateBatchSize) {
-		err := applyBatch(ctx, db, nil, nil, batch, prog)
+		err := applyBatch(ctx, db, nil, batch, prog)
 		if err != nil {
 			return err
 		}
@@ -799,26 +745,10 @@ func applyChanges(ctx context.Context, db *sql.DB, upserts []scanRec,
 	return nil
 }
-// applyDiskSizes writes the disk_size of each of recs into its record,
+// applyBatch commits one batch of upserts and deletes in a single
-// in batched transactions, and leaves the rest of the record alone.
+// transaction.
 // Progress is rendered on prog (one increment per record).
 func applyDiskSizes(ctx context.Context, db *sql.DB, recs []fileRec,
 	prog *progress,
 ) error {
 	for batch := range slices.Chunk(recs, updateBatchSize) {
 		err := applyBatch(ctx, db, nil, batch, nil, prog)
 		if err != nil {
 			return err
 		}
 	}
 	return nil
 }
 // applyBatch commits one batch of upserts, disk_size updates and
 // deletes in a single transaction.
 func applyBatch(ctx context.Context, db *sql.DB, upserts []scanRec,
-	diskSizes []fileRec, deletes []string, prog *progress,
+	deletes []string, prog *progress,
 ) error {
 	tx, err := db.BeginTx(ctx, nil)
 	if err != nil {
@@ -832,11 +762,6 @@ func applyBatch(ctx context.Context, db *sql.DB, upserts []scanRec,
 		return err
 	}
 	err = execDiskSizes(ctx, tx, diskSizes, prog)
 	if err != nil {
 		return err
 	}
 	err = execDeletes(ctx, tx, deletes, prog)
 	if err != nil {
 		return err
@@ -862,7 +787,7 @@ func execUpserts(ctx context.Context, tx *sql.Tx, upserts []scanRec,
 	defer func() { _ = st.Close() }()
 	for _, r := range upserts {
-		_, err = st.ExecContext(ctx, []byte(r.path), r.size, r.diskSize,
+		_, err = st.ExecContext(ctx, []byte(r.path), r.size,
 			r.mtime.Unix(), r.mtime.Nanosecond(),
 			r.head[:], r.tail[:], r.content[:])
 		if err != nil {
@@ -875,31 +800,6 @@ func execUpserts(ctx context.Context, tx *sql.Tx, upserts []scanRec,
 	return nil
 }
 // execDiskSizes sets the disk_size of the record of each of recs. It
 // does not touch size, so the totals triggers do not fire.
 func execDiskSizes(ctx context.Context, tx *sql.Tx, recs []fileRec,
 	prog *progress,
 ) error {
 	st, err := tx.PrepareContext(ctx,
 		"UPDATE files SET disk_size = ? WHERE path = ?")
 	if err != nil {
 		return fmt.Errorf("prepare disk_size update: %w", err)
 	}
 	defer func() { _ = st.Close() }()
 	for _, r := range recs {
 		_, err = st.ExecContext(ctx, r.diskSize, []byte(r.path))
 		if err != nil {
 			return fmt.Errorf("update disk_size of %s: %w", r.path, err)
 		}
 		prog.increment()
 	}
 	return nil
 }
 // execDeletes removes the records for paths no longer present.
 func execDeletes(ctx context.Context, tx *sql.Tx, deletes []string,
 	prog *progress,
@@ -535,12 +535,17 @@ func TestLoadRowsRefuseWrongSizeHash(t *testing.T) {
 	}
 }
-// queryPlan returns the detail of each line of SQLite's EXPLAIN QUERY
+// TestSignatureRowsNeedNoSort checks that SQLite reads signatureRowsSQL
-// PLAN for query.
+// from the files_signature index alone, with nothing to sort: the
-func queryPlan(t *testing.T, db *sql.DB, query string) []string {
+// first record comes at once, so report's read phase counts each
-	t.Helper()
+// record as it comes rather than waiting on SQLite for all of them.
 func TestSignatureRowsNeedNoSort(t *testing.T) {
 	t.Parallel()
-	rows, err := db.QueryContext(t.Context(), "EXPLAIN QUERY PLAN "+query)
+	db := openTestDB(t)
 	rows, err := db.QueryContext(t.Context(),
 		"EXPLAIN QUERY PLAN "+signatureRowsSQL)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -568,164 +573,12 @@ func queryPlan(t *testing.T, db *sql.DB, query string) []string {
 		t.Fatal(err)
 	}
 	return plan
 }
 // TestSignatureRowsNeedNoSort checks that SQLite reads signatureRowsSQL
 // from the files_signature index alone, with nothing to sort: the
 // first record comes at once, so report's read phase counts each
 // record as it comes rather than waiting on SQLite for all of them.
 func TestSignatureRowsNeedNoSort(t *testing.T) {
 	t.Parallel()
 	db := openTestDB(t)
 	plan := queryPlan(t, db, signatureRowsSQL)
 	want := []string{"SCAN files USING COVERING INDEX files_signature"}
 	if !slices.Equal(plan, want) {
 		t.Errorf("query plan = %q, want %q", plan, want)
 	}
 }
 // TestCountsReadOnlyTotals checks that SQLite answers the queries for
 // the number of records and their total size from the one row of
 // totals. A plan that reads files or its index reads every record.
 func TestCountsReadOnlyTotals(t *testing.T) {
 	t.Parallel()
 	db := openTestDB(t)
 	for _, query := range []string{recordCountSQL, databaseCountsSQL} {
 		plan := queryPlan(t, db, query)
 		want := []string{"SCAN totals"}
 		if !slices.Equal(plan, want) {
 			t.Errorf("query plan of %q = %q, want %q", query, plan, want)
 		}
 	}
 }
 // TestCountsComeFromTotals sets the row of totals to numbers that files
 // does not hold, then checks that scan's load phase, the read phases of
 // trees and report, and info each report the numbers from totals.
 func TestCountsComeFromTotals(t *testing.T) {
 	t.Parallel()
 	// files is empty, so a count over files gives 0 records of 0 bytes.
 	const records, size = 7, 9000
 	db := openTestDB(t)
 	_, err := db.ExecContext(t.Context(),
 		"UPDATE totals SET records = ?, size = ?", records, size)
 	if err != nil {
 		t.Fatal(err)
 	}
 	scanTotal, err := countRecords(t.Context(), db)
 	if err != nil {
 		t.Fatal(err)
 	}
 	var treesTotal, reportTotal int64
 	err = loadFileRows(t.Context(), db,
 		func(n int64) { treesTotal = n }, func(scanRec) {})
 	if err != nil {
 		t.Fatal(err)
 	}
 	err = loadSignatureRows(t.Context(), db,
 		func(n int64) { reportTotal = n },
 		func(scanRec) error { return nil })
 	if err != nil {
 		t.Fatal(err)
 	}
 	info, err := readDatabaseCounts(t.Context(), db)
 	if err != nil {
 		t.Fatal(err)
 	}
 	for name, got := range map[string]int64{
 		"scan's load":   scanTotal,
 		"trees' read":   treesTotal,
 		"report's read": reportTotal,
 		"info":          info.records,
 	} {
 		if got != records {
 			t.Errorf("%s: %d records, want %d from totals",
 				name, got, records)
 		}
 	}
 	if info.size != size {
 		t.Errorf("info: size %d, want %d from totals", info.size, size)
 	}
 }
 // assertTotalsMatchFiles fails unless the row of totals holds the
 // number of records and the sizes of all records added up, as counted
 // over files.
 func assertTotalsMatchFiles(t *testing.T, db *sql.DB) {
 	t.Helper()
 	got, err := readDatabaseCounts(t.Context(), db)
 	if err != nil {
 		t.Fatal(err)
 	}
 	var records, size int64
 	err = db.QueryRowContext(t.Context(),
 		"SELECT COUNT(*), COALESCE(SUM(size), 0) FROM files").
 		Scan(&records, &size)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if got.records != records || got.size != size {
 		t.Errorf("totals = %d records of %d bytes, files holds %d of %d",
 			got.records, got.size, records, size)
 	}
 }
 // TestTotalsMatchFiles scans the smoke tree, rescans it after two files
 // change size, and rescans it after two files are removed. After each
 // scan the row of totals must agree with files.
 func TestTotalsMatchFiles(t *testing.T) {
 	t.Parallel()
 	dir := buildSmokeTree(t)
 	db := openTestDB(t)
 	syncTree(t, db, dir)
 	assertTotalsMatchFiles(t, db)
 	writeFile(t, dir, "a/one.bin", pattern(10, 2500))
 	writeFile(t, dir, "t1/f1", pattern(30, 1000))
 	if st := syncTree(t, db, dir); st.updated != 2 {
 		t.Fatalf("rescan stats = %+v, want 2 updated", st)
 	}
 	assertTotalsMatchFiles(t, db)
 	for _, name := range []string{"a/unique.bin", "t2/sub/f2"} {
 		err := os.Remove(filepath.Join(dir, name))
 		if err != nil {
 			t.Fatal(err)
 		}
 	}
 	if st := syncTree(t, db, dir); st.removed != 2 {
 		t.Fatalf("rescan stats = %+v, want 2 removed", st)
 	}
 	assertTotalsMatchFiles(t, db)
 }
 func TestApplyChangesRoundTrip(t *testing.T) {
 	t.Parallel()
@@ -17,9 +17,7 @@ import (
 func TestDefaultExcludes(t *testing.T) {
 	t.Parallel()
-	// README "Rules for the walk": the Linux and macOS lists, and none
+	// README "Rules for the walk": each system's list.
 	// on any other system. The Windows list exists in the code only: the
 	// binary does not build for Windows, so the README leaves it out.
 	cases := map[string][]string{
 		goosLinux: {"/proc", "/sys", "/dev", "/run", "/tmp", "/var/tmp"},
 		goosDarwin: {
@@ -26,11 +26,11 @@ func infoPhase(name string) string {
 // it. Any database problem, including a missing database, is fatal.
 //
 // The work runs in two phases, each under a progress display of its
-// own on stderr: open (open the database) and count (read the number of
+// own on stderr: open (open the database) and count (count the records,
-// records and their total size from the totals table). Each display
+// with one query). Each display ends before the next phase starts, and
-// ends before the next phase starts, and before an error is returned
+// before an error is returned to be printed. The details are written
-// to be printed. The details are written once the last display has
+// once the last display has ended, so no display is drawn while they
-// ended, so no display is drawn while they are written.
+// are written.
 func runInfo(ctx context.Context, stdout io.Writer) error {
 	dbPath, source, err := databasePath()
 	if err != nil {
@@ -56,7 +56,7 @@ func runInfo(ctx context.Context, stdout io.Writer) error {
 	defer func() { _ = db.Close() }()
-	// One row holds both counts, so the phase never has a total.
+	// One query counts everything, so the phase never has a total.
 	prog = newProgress(progressParams{
 		label: infoPhase("count"), total: -1,
 		waitingFor: countingRecords,
@@ -180,9 +180,9 @@ func capture(t *testing.T, std **os.File) func() string {
 }
 // brokenDatabase writes a database that opens cleanly and passes the
-// schema-version check but has no tables, so the first query fails
+// schema-version check but has no files table, so the first query
-// with the database already open: a fatal error on a path that owns an
+// fails with the database already open: a fatal error on a path that
-// open database. It closes the database the way scan does.
+// owns an open database. It closes the database the way scan does.
 func brokenDatabase(t *testing.T) string {
 	t.Helper()
@@ -265,9 +265,8 @@ func TestRunFatalAfterOpenClosesDatabase(t *testing.T) {
 			assertFatalOutput(t, stderr.String(), stdout())
 			// Proof that the failure happened after the open: only a
-			// query against the opened database can report this. Each
+			// query against the opened database can report this.
-			// subcommand's first query reads totals.
+			if !strings.Contains(stderr.String(), "no such table: files") {
 			if !strings.Contains(stderr.String(), "no such table: totals") {
 				t.Errorf("stderr = %q, want the failure to come from a "+
 					"query on the open database", stderr.String())
 			}
@@ -394,7 +393,7 @@ func TestRunNamesRelativeDatabase(t *testing.T) {
 }
 func TestRunUsesDatabaseThroughSymlinkedDirectory(t *testing.T) {
-	// README §Settings: the path names the file exactly. With link a
+	// README §Database: the path names the file exactly. With link a
 	// symlink to the directory real/sub, link/../db.sqlite names
 	// real/db.sqlite, not db.sqlite beside link. Every subcommand must
 	// use that file, relative or absolute, and its first line must name
@@ -649,7 +648,7 @@ func TestRunUsageErrors(t *testing.T) {
 }
 func TestRunScanRejectsWorkersBelowOne(t *testing.T) {
-	// README §Settings: --workers below 1 is a usage error reported in
+	// README §scan mode: --workers below 1 is a usage error reported in
 	// one line on stderr, before the scan opens the database.
 	for _, workers := range []string{"0", "-1"} {
 		t.Run(workers, func(t *testing.T) {
@@ -687,8 +686,8 @@ func TestRunScanRejectsWorkersBelowOne(t *testing.T) {
 func TestRunHelp(t *testing.T) {
 	t.Parallel()
-	// README §Settings: help goes to stderr, exits 0, and leaves stdout
+	// README §Subcommands: help goes to stderr, exits 0, and leaves
-	// empty.
+	// stdout empty.
 	cases := [][]string{{"--help"}, {"-h"}, {cmdScan, "--help"}}
 	for _, args := range cases {
@@ -714,8 +713,8 @@ func TestRunHelp(t *testing.T) {
 func TestRunVersion(t *testing.T) {
 	t.Parallel()
-	// README §Settings: the version is one line on stdout, with nothing
+	// README §Subcommands: the version is one line on stdout, with
-	// on stderr, and exits 0.
+	// nothing on stderr, and exits 0.
 	info, _ := debug.ReadBuildInfo()
 	for _, arg := range []string{"--version", "-v"} {
@@ -774,8 +773,8 @@ func TestBuildVersion(t *testing.T) {
 func TestRunVersionWriteFailureIsFatal(t *testing.T) {
 	t.Parallel()
-	// README §Error handling: a failed write to stdout is a fatal error,
+	// README §Error handling: a stdout write failure exits 1, reported
-	// exit 1, reported on stderr starting with "sfdupes:".
+	// in one line on stderr.
 	var stderr bytes.Buffer
 	code := run([]string{"--version"}, failingWriter{}, &stderr)
@@ -818,23 +817,6 @@ func scanFixture(t *testing.T) []string {
 	return dupes
 }
 // storedDiskSize returns the disk_size of the record for path in the
 // database at dbPath. A test of a trees run compares with this rather
 // than with a new lstat, which on ZFS can differ from the scan's (see
 // diskSizeOf).
 func storedDiskSize(t *testing.T, dbPath, path string) int64 {
 	t.Helper()
 	db, err := openReportDatabase(t.Context(), dbPath)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer func() { _ = db.Close() }()
 	return recordByPath(t, dbRecords(t, db), path).diskSize
 }
 // scanOK runs scan over operands, fails the test unless it exits 0 with
 // nothing on stdout, and returns everything it printed to stderr.
 func scanOK(t *testing.T, operands ...string) string {
@@ -946,21 +928,24 @@ func TestRunScanWalksOperandUnderSymlinkOperand(t *testing.T) {
 }
 func TestRunScanSkipsZFSOperand(t *testing.T) {
-	zfs := filepath.Join(t.TempDir(), ".zfs")
+	path := testDBPath(t)
 	f := writeFile(t, zfs, "snapshot/hourly/f", pattern(1, 10))
 	// No scan records a file inside a .zfs directory, so the record
 	// beneath the operand is written straight into the database.
 	path := seedDatabase(t, []scanRec{{size: 10, path: f}})
 	t.Setenv(databaseEnv, path)
 	zfs := filepath.Join(t.TempDir(), ".zfs")
 	snapshot := filepath.Join(zfs, "snapshot", "hourly")
 	f := writeFile(t, snapshot, "f", pattern(1, 10))
 	// An operand beneath a .zfs directory is walked, because it is not
 	// itself named .zfs.
 	scanOK(t, snapshot)
 	assertOperandSkipped(t, path, zfs, ".zfs directory", f)
 }
 // assertOperandSkipped scans operand alone and checks that it is skipped
 // as kind: a warning naming it, one skip in the summary, exit 0, and the
-// record for kept, stored beneath operand before this scan, still in the
+// record for kept, which an earlier scan stored beneath operand, still
-// database at dbPath.
+// in the database at dbPath.
 func assertOperandSkipped(t *testing.T, dbPath, operand, kind,
 	kept string,
 ) {
@@ -989,121 +974,6 @@ func assertOperandSkipped(t *testing.T, dbPath, operand, kind,
 	recordByPath(t, dbRecords(t, db), kept)
 }
 // TestRunScanSkipsOperandInsideZFS scans a directory inside a .zfs
 // directory, first alone and then under another operand. Each time it
 // is warned about and counted as skipped, and nothing in it is walked.
 // The other operand is scanned as usual.
 func TestRunScanSkipsOperandInsideZFS(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := t.TempDir()
 	hourly := filepath.Join(dir, ".zfs", "snapshot", "hourly")
 	writeFile(t, hourly, "f", pattern(1, 10))
 	f := writeFile(t, dir, "f", pattern(2, 10))
 	warning := "walk " + hourly + ": skipping operand inside a .zfs directory\n"
 	for _, tc := range []struct {
 		operands []string
 		summary  string
 	}{
 		{
 			[]string{hourly},
 			"scan: 0 files seen (0 added, 0 updated, 0 removed, " +
 				"0 unchanged), 1 skipped\n",
 		},
 		{
 			[]string{dir, hourly},
 			"scan: 1 files seen (1 added, 0 updated, 0 removed, " +
 				"0 unchanged), 1 skipped\n",
 		},
 	} {
 		stderr := scanOK(t, tc.operands...)
 		if !strings.Contains(stderr, warning) ||
 			!strings.Contains(stderr, tc.summary) {
 			t.Errorf("scan %q: stderr = %q, want %q and %q", tc.operands,
 				stderr, warning, tc.summary)
 		}
 	}
 	db, err := openDB(path, reportParams)
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { _ = db.Close() })
 	if got := recordPaths(dbRecords(t, db)); !slices.Equal(got, []string{f}) {
 		t.Errorf("records = %q, want %q", got, []string{f})
 	}
 }
 // TestRunScanSkipsOperandThroughSymlinkIntoZFS scans snaps/daily, where
 // snaps is a symlink to pool/.zfs/snapshot. The operand is warned about
 // by the path given, counted as skipped, and not walked.
 func TestRunScanSkipsOperandThroughSymlinkIntoZFS(t *testing.T) {
 	t.Setenv(databaseEnv, testDBPath(t))
 	dir := t.TempDir()
 	writeFile(t, dir, "pool/.zfs/snapshot/daily/f", pattern(1, 10))
 	snaps := filepath.Join(dir, "snaps")
 	err := os.Symlink(filepath.Join(dir, "pool", ".zfs", "snapshot"), snaps)
 	if err != nil {
 		t.Fatal(err)
 	}
 	daily := filepath.Join(snaps, "daily")
 	stderr := scanOK(t, daily)
 	warning := "walk " + daily + ": skipping operand inside a .zfs directory\n"
 	summary := "scan: 0 files seen (0 added, 0 updated, 0 removed, " +
 		"0 unchanged), 1 skipped\n"
 	if !strings.Contains(stderr, warning) ||
 		!strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q and %q", stderr, warning, summary)
 	}
 }
 // TestRunScanWalksOperandThroughSymlink scans data/daily, where data is
 // a symlink to a directory outside any .zfs directory. The operand is
 // scanned as usual, and its file is recorded by the path given.
 func TestRunScanWalksOperandThroughSymlink(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := t.TempDir()
 	writeFile(t, dir, "pool/data/daily/f", pattern(1, 10))
 	data := filepath.Join(dir, "data")
 	err := os.Symlink(filepath.Join(dir, "pool", "data"), data)
 	if err != nil {
 		t.Fatal(err)
 	}
 	daily := filepath.Join(data, "daily")
 	stderr := scanOK(t, daily)
 	summary := "scan: 1 files seen (1 added, 0 updated, 0 removed, " +
 		"0 unchanged), 0 skipped\n"
 	if !strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q", stderr, summary)
 	}
 	db, err := openDB(path, reportParams)
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { _ = db.Close() })
 	recordByPath(t, dbRecords(t, db), filepath.Join(daily, "f"))
 }
 func TestRunReportSucceeds(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
@@ -1158,9 +1028,8 @@ func TestRunTreesSucceeds(t *testing.T) {
 	// The two directories holding the duplicate pair are duplicate
 	// trees of each other.
-	want := "first\tdupe\tfiles\tsize\tdisk_size\n" +
+	want := "first\tdupe\tfiles\tsize\n" +
-		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\t" +
+		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\n"
 		strconv.FormatInt(storedDiskSize(t, path, dupes[1]), 10) + "\n"
 	if got := stdout.String(); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
@@ -1194,10 +1063,9 @@ func TestRunReportsNeedOnlyReadAccess(t *testing.T) {
 	cases := map[string]string{
 		cmdReport: "first\tdupe\tsize\n" +
 			dupes[0] + "\t" + dupes[1] + "\t300\n",
-		cmdTrees: "first\tdupe\tfiles\tsize\tdisk_size\n" +
+		cmdTrees: "first\tdupe\tfiles\tsize\n" +
 			filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) +
-			"\t1\t300\t" +
+			"\t1\t300\n",
 			strconv.FormatInt(storedDiskSize(t, path, dupes[1]), 10) + "\n",
 	}
 	for name, want := range cases {
@@ -1232,11 +1100,8 @@ func assertRunsUseDatabase(t *testing.T, dir, name string) {
 		t.Errorf("report stdout = %q, want %q", got, want)
 	}
-	diskSize := storedDiskSize(t, filepath.Join(dir, name), dupes[1])
+	want = "first\tdupe\tfiles\tsize\n" +
-
+		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\n"
 	want = "first\tdupe\tfiles\tsize\tdisk_size\n" +
 		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\t" +
 		strconv.FormatInt(diskSize, 10) + "\n"
 	if got := runStdout(t, cmdTrees); got != want {
 		t.Errorf("trees stdout = %q, want %q", got, want)
 	}
@@ -1257,7 +1122,7 @@ func assertRunsUseDatabase(t *testing.T, dir, name string) {
 }
 func TestRunDatabasePathUsedAsGiven(t *testing.T) {
-	// README §Settings: the path names the database file exactly. In
+	// README §Database: the path names the database file exactly. In
 	// SQLite's connection string an unescaped ? or # would end the file
 	// name and % would start an escape, and a path starting with //
 	// could be read as a host name. %25 is a valid escape, so unescaped
@@ -1302,8 +1167,9 @@ func holdScanLock(t *testing.T, path string) {
 }
 func TestRunSecondScanFails(t *testing.T) {
-	// README §Database: a second scan that finds the lock held fails
+	// README §Database: while one scan holds the lock, a second scan
-	// at once, naming the lock file, without opening the database.
+	// fails at once, naming the lock file, without opening the
 	// database.
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
@@ -1362,7 +1228,7 @@ func assertSecondScanFails(t *testing.T, path string) {
 }
 func TestRunSecondScanThroughSymlinkFails(t *testing.T) {
-	// README §Database: a path through a symlink names the same lock
+	// README §Database: every path to one database names the same lock
 	// file, so while a scan holds it through one path, a scan through
 	// another fails, naming the lock file beside the database's real
 	// path.
@@ -1467,8 +1333,8 @@ func TestRunReportsDuringScan(t *testing.T) {
 }
 func TestRunStdoutClosedIsFatal(t *testing.T) {
-	// README §Error handling: a failed write to stdout is a fatal error,
+	// README §Error handling: a stdout write failure exits 1, reported
-	// exit 1, reported on stderr starting with "sfdupes:".
+	// in one line on stderr.
 	for _, name := range []string{cmdReport, cmdTrees, cmdInfo} {
 		t.Run(name, func(t *testing.T) {
 			t.Setenv(databaseEnv, testDBPath(t))
@@ -60,7 +60,7 @@ const fallbackWidth = 80
 const spinnerMargin = 5
 // countingRecords is what the display of a phase that reads the records
-// says until it has the number of records, its total.
+// says while it counts them, before it has its total.
 const countingRecords = "counting the records"
 // openPhase is the name of the phase in which report, trees and info
@@ -21,16 +21,14 @@ const minGroupSize = 2
 // scanRec is one file record from the database. The signature (size,
 // head, tail, content) is the duplicate key; mtime is informational
-// only and used by scan for change detection. diskSize is the bytes the
+// only and used by scan for change detection.
 // file takes on disk, which trees adds up.
 type scanRec struct {
-	size     int64
+	size    int64
-	diskSize int64
+	mtime   time.Time
-	mtime    time.Time
+	head    [sha256.Size]byte
-	head     [sha256.Size]byte
+	tail    [sha256.Size]byte
-	tail     [sha256.Size]byte
+	content [sha256.Size]byte
-	content  [sha256.Size]byte
+	path    string
 	path     string
 }
 // reportPhase names one phase of report with its place among all of
@@ -47,11 +45,11 @@ func reportPhase(name string) string {
 // problem, including a missing database, is fatal.
 //
 // The work runs in two phases, each under a progress display of its
-// own on stderr: open (open the database) and read (read the number of
+// own on stderr: open (open the database) and read (count the records,
-// records from the totals table, then read the records in signature
+// then read them in signature order, writing each size's duplicate
-// order, writing each size's duplicate groups to stdout once that size
+// groups to stdout once that size is read; see readReport). Each
-// is read; see readReport). Each display ends before the next phase
+// display ends before the next phase starts, and before an error is
-// starts, and before an error is returned to be printed.
+// returned to be printed.
 func runReport(ctx context.Context, stdout io.Writer) error {
 	dbPath, source, err := databasePath()
 	if err != nil {
@@ -38,8 +38,8 @@ func awkwardPairRecs() []scanRec {
 	h, tl, c := testHash("h"), testHash("t"), testHash("c")
 	return []scanRec{
-		{size: 5, diskSize: 4096, head: h, tail: tl, content: c, path: "/d/A/f"},
+		{size: 5, head: h, tail: tl, content: c, path: "/d/A/f"},
-		{size: 5, diskSize: 4096, head: h, tail: tl, content: c, path: awkwardDir + "/f"},
+		{size: 5, head: h, tail: tl, content: c, path: awkwardDir + "/f"},
 	}
 }
@@ -52,26 +52,23 @@ const workQueueDepth = 1024
 // has already printed its line, so run prints nothing more.
 var errInterrupted = errors.New("scan interrupted")
-// fileRec carries one statted file between the scan phases. diskSize is
+// fileRec carries one statted file between the scan phases. dev and
-// the bytes the file takes on disk. dev and ino identify the underlying
+// ino identify the underlying inode so hard-linked paths can share
-// inode so hard-linked paths can share one read; both are zero when the
+// one read; both are zero when the platform exposes no inode.
 // platform exposes no inode.
 type fileRec struct {
-	path     string
+	path  string
-	size     int64
+	size  int64
-	diskSize int64
+	mtime time.Time
-	mtime    time.Time
+	dev   uint64
-	dev      uint64
+	ino   uint64
 	ino      uint64
 }
 // fileMeta is the in-memory index entry for one existing database
-// record: what the walk compares the file with. Hashes stay on disk; at
+// record: just enough for change detection. Hashes stay on disk; at
 // tens of millions of records they would dominate the scan's memory.
 type fileMeta struct {
-	size     int64
+	size  int64
-	diskSize int64
+	mtime time.Time
 	mtime    time.Time
 }
 // scanUnit is what every scan phase counts, as its progress display
@@ -342,12 +339,11 @@ type scanStats struct {
 // whatever remains after the walk and hash phases is deleted by the
 // update phase.
 type scanState struct {
-	db        *sql.DB
+	db       *sql.DB
-	existing  map[string]fileMeta
+	existing map[string]fileMeta
-	toHash    []fileRec // new and changed files: must be read
+	toHash   []fileRec // new and changed files: must be read
-	diskSizes []fileRec // unchanged files whose disk_size changed
+	batch    []scanRec
-	batch     []scanRec
+	st       scanStats
 	st        scanStats
 }
 // syncScan synchronizes the database with the filesystem under roots;
@@ -387,8 +383,7 @@ func (s *scanState) runPhases(ctx context.Context, roots []string,
 ) error {
 	// Types and filesystems are checked before pruning so that an
 	// operand under a dropped one is still scanned, not dropped as lying
-	// under it, and so that an operand inside a .zfs directory gets its
+	// under it.
 	// warning even when it lies under another operand.
 	roots = pruneRoots(s.walkableRoots(roots, rules), oneFS, rules,
 		deviceOfPath)
@@ -416,15 +411,15 @@ func (s *scanState) runPhases(ctx context.Context, roots []string,
 }
 // walkableRoots returns the operands the walk can start from: regular
-// files, and directories not named .zfs, none of them inside a
+// files, and directories not named .zfs. Every other operand is warned
-// directory named .zfs. Every other operand is warned about, counted as
+// about, counted as skipped, and dropped. A dropped operand is no
-// skipped, and dropped. A dropped operand is no longer a root, so the
+// longer a root, so the records stored beneath it are treated as if it
-// records stored beneath it are treated as if it had not been given:
+// had not been given: those under no other root count as outside the
-// those under no other root count as outside the roots and are not
+// roots and are not deleted as unverified. An operand on a filesystem
-// deleted as unverified. An operand on a filesystem in rules that is not
+// in rules that is not persistent is dropped the same way, with a line
-// persistent is dropped the same way, with a line saying so that is not
+// saying so that is not a warning, and is not counted as skipped. An
-// a warning, and is not counted as skipped. An operand that fails lstat
+// operand that fails lstat here is kept, and the walk warns about it
-// here is kept, and the walk warns about it unless it no longer exists.
+// unless it no longer exists.
 func (s *scanState) walkableRoots(roots []string, rules walkRules) []string {
 	kept := make([]string, 0, len(roots))
@@ -459,8 +454,8 @@ func (s *scanState) walkableRoots(roots []string, rules walkRules) []string {
 // included, so its display counts against the number of records.
 func (s *scanState) loadIndex(ctx context.Context, roots []string) error {
 	// Indexing tens of millions of records takes real time; without a
-	// display the scan looks hung before the walk begins. The number of
+	// display the scan looks hung before the walk begins. Counting them
-	// records, read first, gives the display its total.
+	// first gives the display its total.
 	prog := newProgress(progressParams{
 		label: scanPhase("load"), unit: scanUnit, total: -1,
 		waitingFor: countingRecords, stalledOn: "db",
@@ -476,24 +471,24 @@ func (s *scanState) loadIndex(ctx context.Context, roots []string) error {
 	s.existing = make(map[string]fileMeta)
-	return loadFileMeta(ctx, s.db, func(path string, m fileMeta) {
+	return loadFileMeta(ctx, s.db,
-		prog.increment()
+		func(path string, size int64, mtime time.Time) {
 			prog.increment()
-		if underAnyRoot(path, roots) {
+			if underAnyRoot(path, roots) {
-			s.existing[path] = m
+				s.existing[path] = fileMeta{size: size, mtime: mtime}
-		}
+			}
-	})
+		})
 }
 // walkPhase drains the walk and queues every new or changed file for
-// the hash phase. An unchanged file is not read, and its record counts
+// the hash phase. An unchanged file needs nothing more, and its record
-// as verified. When its disk_size differs from the record's, it is
+// counts as verified. A record at or below a path the walk left out,
-// queued for the update phase, which writes the new disk_size. A record
+// because -x stopped at it, it is a default exclude, or it is not on a
-// at or below a path the walk left out, because -x stopped at it, it is
+// persistent filesystem, counts as outside the roots: it is not
-// a default exclude, or it is not on a persistent filesystem, counts as
+// deleted. That does not hold below a root at or inside that path,
-// outside the roots: it is not deleted. That does not hold below a root
+// since that root's own walk verifies the records below it; nor is a
-// at or inside that path, since that root's own walk verifies the
+// line printed for such a root.
 // records below it; nor is a line printed for such a root.
 func (s *scanState) walkPhase(events <-chan walkEvent, roots []string) {
 	// The records the last scan left under the roots estimate how many
 	// files the walk will find. A first scan has none, and no estimate.
@@ -551,13 +546,6 @@ func (s *scanState) walkPhase(events <-chan walkEvent, roots []string) {
 		delete(s.existing, ev.rec.path)
 		s.st.unchanged++
 		// The space a file takes on disk can change while its size and
 		// mtime stay the same. ZFS, for one, counts a new file's blocks
 		// only seconds after the write.
 		if old.diskSize != ev.rec.diskSize {
 			s.diskSizes = append(s.diskSizes, ev.rec)
 		}
 	}
 	prog.finish()
@@ -706,13 +694,12 @@ func (s *scanState) recordRun(ctx context.Context, r hashResult) error {
 		s.resolve(rec.path)
 		s.batch = append(s.batch, scanRec{
-			size:     rec.size,
+			size:    rec.size,
-			diskSize: rec.diskSize,
+			mtime:   rec.mtime,
-			mtime:    rec.mtime,
+			head:    r.head,
-			head:     r.head,
+			tail:    r.tail,
-			tail:     r.tail,
+			content: r.content,
-			content:  r.content,
+			path:    rec.path,
 			path:     rec.path,
 		})
 	}
@@ -728,7 +715,7 @@ func (s *scanState) commitFullBatch(ctx context.Context) error {
 		return nil
 	}
-	err := applyBatch(ctx, s.db, s.batch, nil, nil, nil)
+	err := applyBatch(ctx, s.db, s.batch, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -739,10 +726,9 @@ func (s *scanState) commitFullBatch(ctx context.Context) error {
 }
 // updatePhase writes the scan's tail under one progress display: the
-// final partial batch of hashed records, the new disk_size of every
+// final partial batch of hashed records, and deletions for every record
-// unchanged file whose disk_size changed, and deletions for every
+// the scan did not verify (vanished files, plus paths that failed to
-// record the scan did not verify (vanished files, plus paths that
+// stat or hash).
 // failed to stat or hash).
 func (s *scanState) updatePhase(ctx context.Context) error {
 	deletes := make([]string, 0, len(s.existing))
 	for path := range s.existing {
@@ -754,7 +740,7 @@ func (s *scanState) updatePhase(ctx context.Context) error {
 	s.st.removed = len(deletes)
-	total := len(s.batch) + len(s.diskSizes) + len(deletes)
+	total := len(s.batch) + len(deletes)
 	prog := newProgress(progressParams{
 		label: scanPhase("update"), unit: scanUnit, total: int64(total),
 		stalledOn: "db",
@@ -769,11 +755,6 @@ func (s *scanState) updatePhase(ctx context.Context) error {
 	s.batch = nil
 	err = applyDiskSizes(ctx, s.db, s.diskSizes, prog)
 	if err != nil {
 		return err
 	}
 	return applyChanges(ctx, s.db, nil, deletes, prog)
 }
@@ -893,24 +874,9 @@ func sendEvent(ctx context.Context, events chan<- walkEvent,
 // operandWarning returns the one-line warning for an operand the walk
 // does not start from, naming the path and what it is, or "" for one it
-// does: a regular file, or a directory not named .zfs, that is not
+// does: a regular file, or a directory not named .zfs. Symlinks are
-// inside a directory named .zfs, neither as given nor with its symlinks
+// never followed, including as operands.
 // resolved. Symlinks are never followed, including as operands.
 func operandWarning(root string, fi fs.FileInfo) string {
 	// The walk never enters a .zfs directory, so it starts from nothing
 	// inside one either, not even through a symlink. An operand whose
 	// symlinks cannot be resolved is checked as given.
 	resolved, err := filepath.EvalSymlinks(root)
 	if err != nil {
 		resolved = root
 	}
 	if slices.Contains(strings.Split(filepath.Dir(root), "/"), ".zfs") ||
 		slices.Contains(strings.Split(filepath.Dir(resolved), "/"), ".zfs") {
 		return fmt.Sprintf("walk %s: skipping operand inside a .zfs directory",
 			root)
 	}
 	var kind string
 	switch mode := fi.Mode(); {
@@ -979,12 +945,11 @@ func seedRoot(ctx context.Context, root string, rules walkRules,
 	dev, ino := inodeOfInfo(fi)
 	rec := fileRec{
-		path:     root,
+		path:  root,
-		size:     fi.Size(),
+		size:  fi.Size(),
-		diskSize: diskSizeOfInfo(fi),
+		mtime: fi.ModTime(),
-		mtime:    fi.ModTime(),
+		dev:   dev,
-		dev:      dev,
+		ino:   ino,
 		ino:      ino,
 	}
 	if !isDatabaseFile(rec, rules) {
@@ -1164,12 +1129,11 @@ func emitFile(ctx context.Context, p string, e fs.DirEntry,
 	dev, ino := inodeOfInfo(info)
 	rec := fileRec{
-		path:     p,
+		path:  p,
-		size:     info.Size(),
+		size:  info.Size(),
-		diskSize: diskSizeOfInfo(info),
+		mtime: info.ModTime(),
-		mtime:    info.ModTime(),
+		dev:   dev,
-		dev:      dev,
+		ino:   ino,
 		ino:      ino,
 	}
 	if !isDatabaseFile(rec, rules) {
@@ -1261,23 +1225,6 @@ func inodeOfInfo(fi fs.FileInfo) (uint64, uint64) {
 	return statDev(st), st.Ino
 }
 // statBlockSize is the unit of st_blocks in an lstat result on Linux and
 // macOS, whatever the filesystem's own block size.
 const statBlockSize = 512
 // diskSizeOfInfo returns the bytes a file takes on disk: its allocated
 // blocks, st_blocks × 512. On a compressed or sparse file it is less
 // than the file's size. It is 0 when the platform exposes no block
 // count.
 func diskSizeOfInfo(fi fs.FileInfo) int64 {
 	st, ok := fi.Sys().(*syscall.Stat_t)
 	if !ok {
 		return 0
 	}
 	return st.Blocks * statBlockSize
 }
 // hashResult carries the hashes computed for one inode run (or the
 // error that prevented computing them) from the pool's workers to the
 // hash phase. Its run leaves out the paths found removed.
@@ -42,24 +42,6 @@ func writeFile(t *testing.T, dir, name string, data []byte) string {
 	return p
 }
 // diskSizeOf returns the bytes the file at path takes on disk, from its
 // own lstat: st_blocks counts 512-byte units. ZFS counts a new file's
 // blocks only seconds after the write, and fsync does not hasten that.
 // A test therefore calls unix.Sync, which waits for it, before the scan
 // whose disk_size it compares with this.
 func diskSizeOf(t *testing.T, path string) int64 {
 	t.Helper()
 	var st syscall.Stat_t
 	err := syscall.Lstat(path, &st)
 	if err != nil {
 		t.Fatal(err)
 	}
 	return st.Blocks * 512
 }
 // pattern returns n bytes of deterministic content seeded by tag.
 func pattern(tag byte, n int) []byte {
 	data := make([]byte, n)
@@ -1082,9 +1064,8 @@ func TestScanOneFilesystemWalksNestedFileOperand(t *testing.T) {
 	}
 }
-// buildSmokeTree recreates the tree of the test under README
+// buildSmokeTree recreates the README smoke-test filesystem layout
-// "Definition of done" with deterministic content and returns the tree
+// with deterministic content and returns the tree root.
 // root.
 func buildSmokeTree(t *testing.T) string {
 	t.Helper()
@@ -1247,9 +1228,9 @@ func TestScanPipeline(t *testing.T) {
 // TestScanProgressNamesEachPhase checks the plain progress lines of a
 // first scan, and of a rescan of one operand holding two of the
 // database's records. Each phase's first line names it with its place
-// among the four: load gets the number of records before reading them,
+// among the four: load counts the records before reading them, and the
-// and the walk estimates its total from the records under its operand,
+// walk estimates its total from the records under its operand, or says
-// or says its time remaining is unknown when there are none.
+// its time remaining is unknown when there are none.
 //
 //nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
 func TestScanProgressNamesEachPhase(t *testing.T) {
@@ -1435,116 +1416,6 @@ func TestScanStoresRawHashes(t *testing.T) {
 	}
 }
 // TestScanStoresDiskSize scans a sparse file, which takes less space on
 // disk than its length, once through its directory and once as the
 // operand itself. Each scan stores the disk_size of the file's lstat.
 func TestScanStoresDiskSize(t *testing.T) {
 	t.Parallel()
 	const length = 1024 * 1024
 	p := sparseFile(t, t.TempDir(), "sparse", length)
 	pokeAt(t, p, 0, []byte("x"))
 	unix.Sync() // see diskSizeOf
 	want := diskSizeOf(t, p)
 	if want == 0 || want >= length {
 		t.Fatalf("the file takes %d bytes on disk, want more than none "+
 			"and fewer than its length %d", want, length)
 	}
 	for _, operand := range []string{filepath.Dir(p), p} {
 		db := openTestDB(t)
 		syncTree(t, db, operand)
 		got := recordByPath(t, dbRecords(t, db), p).diskSize
 		if got != want {
 			t.Errorf("scan of %s: disk_size = %d, want %d",
 				operand, got, want)
 		}
 	}
 }
 // TestSyncScanRewriteUpdatesDiskSize writes into the hole of a scanned
 // sparse file and moves its mtime on. The rescan hashes the file again
 // and rewrites its record with the new disk_size.
 func TestSyncScanRewriteUpdatesDiskSize(t *testing.T) {
 	t.Parallel()
 	dir := t.TempDir()
 	db := openTestDB(t)
 	p := sparseFile(t, dir, "sparse", 1024*1024)
 	pokeAt(t, p, 0, []byte("x"))
 	syncTree(t, db, dir)
 	before := recordByPath(t, dbRecords(t, db), p).diskSize
 	pokeAt(t, p, 512*1024, pattern(7, 64*1024))
 	// The write may leave the mtime the scan recorded; a later one makes
 	// the rescan read the file again.
 	later := time.Now().Add(time.Hour)
 	err := os.Chtimes(p, later, later)
 	if err != nil {
 		t.Fatal(err)
 	}
 	unix.Sync() // see diskSizeOf
 	want := diskSizeOf(t, p)
 	if want == before {
 		t.Fatalf("the file still takes %d bytes on disk after the write "+
 			"into its hole", want)
 	}
 	st := syncTree(t, db, dir)
 	if st != (scanStats{walked: 1, updated: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 updated", st)
 	}
 	got := recordByPath(t, dbRecords(t, db), p).diskSize
 	if got != want {
 		t.Errorf("disk_size = %d, want %d", got, want)
 	}
 }
 // TestSyncScanUnchangedUpdatesDiskSize gives a file's record a
 // disk_size the file does not have, as when ZFS had not yet counted the
 // file's blocks at the last scan. The rescan writes the file's own
 // disk_size into the record without reading the file again.
 func TestSyncScanUnchangedUpdatesDiskSize(t *testing.T) {
 	t.Parallel()
 	dir := t.TempDir()
 	db := openTestDB(t)
 	p := writeFile(t, dir, "a.bin", pattern(1, 500))
 	syncTree(t, db, dir)
 	// lstat counts 512-byte units, so no file takes 1 byte on disk.
 	_, err := db.ExecContext(t.Context(),
 		"UPDATE files SET disk_size = 1 WHERE path = ?", []byte(p))
 	if err != nil {
 		t.Fatal(err)
 	}
 	unix.Sync() // see diskSizeOf
 	// A file read again would count as updated.
 	st := syncTree(t, db, dir)
 	if st != (scanStats{walked: 1, unchanged: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 unchanged", st)
 	}
 	got := recordByPath(t, dbRecords(t, db), p).diskSize
 	if want := diskSizeOf(t, p); got != want {
 		t.Errorf("disk_size = %d, want %d", got, want)
 	}
 }
 // TestSyncScanSameSecondRewrite rewrites a file in place at the same
 // size with an mtime later in the same second as the recorded one: the
 // next scan must notice the change and re-hash the file. The operand is
@@ -22,10 +22,6 @@ type treeNode struct {
 	digest    [sha256.Size]byte
 	fileCount int64
 	totalSize int64
 	// diskSize is the bytes the directory's files take on disk. Two
 	// copies of one tree have the same totalSize, but their diskSize
 	// can differ.
 	diskSize int64
 }
 // treesPhase names one phase of trees with its place among all of them,
@@ -44,11 +40,11 @@ func treesPhase(name string) string {
 // database problem, including a missing database, is fatal.
 //
 // The work runs in four phases, each under a progress display of its
-// own on stderr: open (open the database), read (read the number of
+// own on stderr: open (open the database), read (count the records,
-// records from the totals table, then read the records into the
+// then read them into the hierarchy), group (group the directories by
-// hierarchy), group (group the directories by digest) and write (write
+// digest) and write (write the groups to stdout). Each display ends
-// the groups to stdout). Each display ends before the next phase
+// before the next phase starts, and before an error is returned to be
-// starts, and before an error is returned to be printed.
+// printed.
 func runTrees(ctx context.Context, stdout io.Writer) error {
 	dbPath, source, err := databasePath()
 	if err != nil {
@@ -143,16 +139,15 @@ func readTree(ctx context.Context, db *sql.DB,
 // writeTreeGroups writes dupes to stdout as TSV, a header line and then
 // a row for every member of each group but its first, counting each
-// group on prog once its rows are written. The disk_size column is the
+// group on prog once its rows are written. stdout may be the terminal
-// dupe's own. stdout may be the terminal prog is drawn on, so the lines
+// prog is drawn on, so the lines go through prog's writer. It returns
-// go through prog's writer. It returns the number of rows (dupe trees)
+// the number of rows (dupe trees) and the bytes they could reclaim.
 // and the bytes they could reclaim.
 func writeTreeGroups(stdout io.Writer, dupes [][]*treeNode,
 	prog *progress,
 ) (int, int64, error) {
 	out := prog.writer(stdout)
-	_, err := fmt.Fprintln(out, "first\tdupe\tfiles\tsize\tdisk_size")
+	_, err := fmt.Fprintln(out, "first\tdupe\tfiles\tsize")
 	if err != nil {
 		return 0, 0, fmt.Errorf("write stdout: %w", err)
 	}
@@ -164,9 +159,9 @@ func writeTreeGroups(stdout io.Writer, dupes [][]*treeNode,
 	for _, g := range dupes {
 		first := g[0]
 		for _, n := range g[1:] {
-			_, err = fmt.Fprintf(out, "%s\t%s\t%d\t%d\t%d\n",
+			_, err = fmt.Fprintf(out, "%s\t%s\t%d\t%d\n",
 				escapePath(first.path), escapePath(n.path),
-				first.fileCount, first.totalSize, n.diskSize)
+				first.fileCount, first.totalSize)
 			if err != nil {
 				return 0, 0, fmt.Errorf("write stdout: %w", err)
 			}
@@ -237,7 +232,6 @@ func (b *treeBuilder) add(r scanRec) {
 	dir.entries = append(dir.entries, fileEntry(name, r))
 	dir.fileCount++
 	dir.totalSize += r.size
 	dir.diskSize += r.diskSize
 }
 // openDir starts the directory called name inside the innermost open
@@ -276,7 +270,6 @@ func (b *treeBuilder) closeTo(n int) {
 			"d\x00"+name+"\x00"+string(dir.digest[:]))
 		dir.parent.fileCount += dir.fileCount
 		dir.parent.totalSize += dir.totalSize
 		dir.parent.diskSize += dir.diskSize
 		b.dirs = append(b.dirs, dir)
 	}
 }
@@ -15,26 +15,20 @@ import (
 const treesOpenLine = "[1/4] open: opening the database, elapsed 0s, " +
 	"remain unknown"
-// smokeTreeRecs mirrors the tree of the test under README "Definition
+// smokeTreeRecs mirrors the README smoke-test tree layout: /d/t1 and
-// of done": /d/t1 and /d/t2 are identical, /d/t3 differs from them only
+// /d/t2 are identical, /d/t3 differs from them only by one filename.
 // by one filename. Each file takes one 4 KiB block on disk.
 func smokeTreeRecs() []scanRec {
 	f1Head, f1Tail, f1Content := testHash("f1h"), testHash("f1t"), testHash("f1c")
 	f2Head, f2Tail, f2Content := testHash("f2h"), testHash("f2t"), testHash("f2c")
 	return []scanRec{
-		{size: 3000, diskSize: 4096, head: f1Head, tail: f1Tail,
+		{size: 3000, head: f1Head, tail: f1Tail, content: f1Content, path: "/d/t1/f1"},
-			content: f1Content, path: "/d/t1/f1"},
+		{size: 100, head: f2Head, tail: f2Tail, content: f2Content, path: "/d/t1/sub/f2"},
-		{size: 100, diskSize: 4096, head: f2Head, tail: f2Tail,
+		{size: 3000, head: f1Head, tail: f1Tail, content: f1Content, path: "/d/t2/f1"},
-			content: f2Content, path: "/d/t1/sub/f2"},
+		{size: 100, head: f2Head, tail: f2Tail, content: f2Content, path: "/d/t2/sub/f2"},
-		{size: 3000, diskSize: 4096, head: f1Head, tail: f1Tail,
+		{size: 3000, head: f1Head, tail: f1Tail, content: f1Content, path: "/d/t3/f1"},
-			content: f1Content, path: "/d/t2/f1"},
+		{size: 100, head: f2Head, tail: f2Tail, content: f2Content,
-		{size: 100, diskSize: 4096, head: f2Head, tail: f2Tail,
+			path: "/d/t3/sub/f2renamed"},
 			content: f2Content, path: "/d/t2/sub/f2"},
 		{size: 3000, diskSize: 4096, head: f1Head, tail: f1Tail,
 			content: f1Content, path: "/d/t3/f1"},
 		{size: 100, diskSize: 4096, head: f2Head, tail: f2Tail,
 			content: f2Content, path: "/d/t3/sub/f2renamed"},
 	}
 }
@@ -204,33 +198,13 @@ func TestRunTreesEscapesPaths(t *testing.T) {
 			code, exitOK, stderr.String())
 	}
-	want := "first\tdupe\tfiles\tsize\tdisk_size\n" +
+	want := "first\tdupe\tfiles\tsize\n" +
-		`/d/\tone\ntwo\rthree\\four` + "\t/d/A\t1\t5\t4096\n"
+		`/d/\tone\ntwo\rthree\\four` + "\t/d/A\t1\t5\n"
 	if got := stdout.String(); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
 }
 // TestRunTreesDiskSize runs trees on two copies of a tree whose files
 // take different space on disk. The row's disk_size is the sum over the
 // dupe copy's files, those in its subdirectory included.
 func TestRunTreesDiskSize(t *testing.T) {
 	f, g := testHash("f"), testHash("g")
 	recs := []scanRec{
 		{size: 10, diskSize: 4096, head: f, tail: f, content: f, path: "/a/f"},
 		{size: 20, diskSize: 4096, head: g, tail: g, content: g, path: "/a/sub/g"},
 		{size: 10, diskSize: 512, head: f, tail: f, content: f, path: "/b/f"},
 		{size: 20, diskSize: 1024, head: g, tail: g, content: g, path: "/b/sub/g"},
 	}
 	t.Setenv(databaseEnv, seedDatabase(t, recs))
 	want := "first\tdupe\tfiles\tsize\tdisk_size\n/a\t/b\t2\t30\t1536\n"
 	if got := runStdout(t, cmdTrees); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
 }
 // TestRunTreesProgressNamesEachPhase runs trees on the smoke-test
 // records with stderr not a terminal, and checks every line it prints
 // there. After the line naming the database, each phase prints a line
@@ -252,8 +226,7 @@ func TestRunTreesProgressNamesEachPhase(t *testing.T) {
 			code, exitOK, stderr())
 	}
-	report := "first\tdupe\tfiles\tsize\tdisk_size\n" +
+	report := "first\tdupe\tfiles\tsize\n/d/t1\t/d/t2\t2\t3100\n"
 		"/d/t1\t/d/t2\t2\t3100\t8192\n"
 	if got := stdout.String(); got != report {
 		t.Errorf("stdout = %q, want %q", got, report)
 	}
@@ -318,9 +291,7 @@ func TestWriteTreeGroupsOnTerminal(t *testing.T) {
 		shown = append(shown, line[strings.LastIndex(line, "\r")+1:])
 	}
-	want := []string{
+	want := []string{"first\tdupe\tfiles\tsize", "/d/t1\t/d/t2\t2\t3100"}
 		"first\tdupe\tfiles\tsize\tdisk_size", "/d/t1\t/d/t2\t2\t3100\t8192",
 	}
 	if len(shown) < len(want) || !slices.Equal(shown[:len(want)], want) {
 		t.Errorf("terminal shows lines %q, want %q first", shown, want)
 	}