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 its issue or branch, and every fact the old entries recorded is kept too, in short sentences. 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 10:39:47 +00:00
17 changed files with 1226 additions and 2535 deletions
@@ -29,63 +29,17 @@
 Newest first. An entry ends with its date and its issue or branch, where those
 are known.
 - New subcommand `dwim`. It runs what `sfdupes scan /` runs with no flags, then
  what `sfdupes trees` runs. Its last line on stderr says that `sfdupes trees`
  prints the report again (2026-11-06,
  https://git.eeqj.de/sneak/sfdupes/issues/154)
 - `scan` resolves each operand to its real path, symlinks followed, before the
  walk. A symlink operand is scanned at its target instead of skipped. With
  `/srv/link` a symlink to a directory outside `/srv`, `scan /srv /srv/link/sub`
  walks `sub` on its own instead of dropping it and deleting its records
  (2026-11-06, https://git.eeqj.de/sneak/sfdupes/issues/144)
 - `README.md` and a comment in `scan.go` no longer say ZFS counts a new file's
  blocks only seconds after the write. The count can land in under a second.
  Both now say up to seconds after the write, as the comment on `diskSizeOf` in
  `scan_test.go` does (2026-11-03, https://git.eeqj.de/sneak/sfdupes/issues/152)
 - The three disk size tests in `scan_test.go` no longer fail at random on ZFS.
  `unix.Sync` can return before ZFS has counted a file's blocks, and one ZFS
  commit can take a file through several sizes. The test that needs the size to
  change waits for it, for at most 30 seconds. Each test reads the size before
  and after its scan. The rewrite test rescans until the two reads match, then
  compares exactly. The other two fail only on a `disk_size` outside the two
  reads (2026-11-02, https://git.eeqj.de/sneak/sfdupes/issues/150)
 - `TODO.md` rewritten from scratch by the same rules as `README.md`, sentence by
  sentence. Every completed step is kept, with its date and its issue or branch.
  The policy-compliance checklist of 2026-07-22 is folded into its step
-  (2026-11-02, https://git.eeqj.de/sneak/sfdupes/issues/135)
+  (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.
-  Every statement was checked against the code on `next`. Five comments in
+  Every statement was checked against the code on `next`. Three comments in
-  `main_test.go` cite "Settings", where their rules now live. One comment each
+  `main_test.go` cite "Settings", where their rules now live (2026-10-26,
-  in `scan_test.go`, `trees_test.go` and `exclude_test.go` cites what the README
+  https://git.eeqj.de/sneak/sfdupes/issues/135)
  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
@@ -103,10 +57,10 @@ are known.
  `trees`. Reading 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. Gone are:
    - the 10 MiB and 50 MiB thresholds;
    - the size census, which counted the sizes of every walked file and of every
      record outside the operands. A file was hashed only when the census showed
@@ -119,8 +73,8 @@ are known.
    with a content hash, since every record has all three (2026-10-25,
    https://git.eeqj.de/sneak/sfdupes/issues/132)
- `REPO_POLICIES.md` and the four scripts that pass `CACHEBUST` were copied
+- `REPO_POLICIES.md` and the four scripts that pass `CACHEBUST` copied again
-  again from `sneak/prompts` `next` at `0653579`. Two steps now come before
+  from `sneak/prompts` `next` at `0653579`. Two steps now come before
  `ARG CACHEBUST`:
    - the module download in the `lint`, `test` and `builder` stages of the
      `Dockerfile`;
@@ -136,13 +90,12 @@ are known.
    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
+- Release rule set. Until 1.0, each tip of `main` that passes the build gets the
-  gets the next `v0.0.N` tag. `go install sneak.berlin/go/sfdupes@latest` then
+  next `v0.0.N` tag. `go install sneak.berlin/go/sfdupes@latest` then installs
-  installs it. `go.mod` retracts `v0.0.1`, the early build without a database.
+  it. `go.mod` retracts `v0.0.1`, the early build without a database. When the
-  When the linker set no version, `sfdupes --version` prints the version Go
+  linker set no version, `sfdupes --version` prints the version Go recorded in
-  recorded in the binary. That is the tag, or the pseudo-version of a
+  the binary. That is the tag, or the pseudo-version of a `go install` build. It
-  `go install` build. It prints `dev` only when neither is known. README
+  prints `dev` only when neither is known. README "Install" documented:
  "Install" documented:
    - the rule;
    - what `@main` and `v0.0.1` give;
    - how to check an installed binary.
@@ -196,12 +149,12 @@ are known.
    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.
+- The rate a progress display shows covers the items completed over the last 5
-  When stderr is not a terminal, it covers the items since the line before. It
+  seconds. When stderr is not a terminal, it covers the items since the line
-  falls to 0 while nothing completes. A burst after a wait no longer reads as a
+  before. It falls to 0 while nothing completes. A burst after a wait no longer
-  steady rate of over 1,000 files a second. The time remaining still comes from
+  reads as a steady rate of over 1,000 files a second. The time remaining still
-  the phase's average. Once no item has completed for 10 seconds, the line shows
+  comes from the phase's average. Once no item has completed for 10 seconds, the
-  `stalled` and where the phase waits in place of the rate, as
+  word `stalled` and where the phase waits take the rate's place, as
  `stalled disk/db`. The places are:
    - `disk`;
    - `db`;
@@ -216,12 +169,12 @@ are known.
    - the elapsed time;
    - the ETA, the time remaining.
-    The content phase had one display for its checks and one for its reads. Both
+    On an 80-column terminal, at counts like those of README's example, the
-    lost those words on an 80-column terminal, at counts like those of README's
+    content phase's displays for its checks and its reads lost those words. That
-    example. That happened for most elapsed times and ETAs in minutes. Every
+    happened for most elapsed times and ETAs in minutes. Every other phase kept
-    other phase kept them whenever the elapsed time and the ETA were both in
+    them whenever the elapsed time and the ETA were both in minutes. The content
-    minutes. The content phase writes its last partial batch, the records not
+    phase writes its last partial batch, the records not yet written, under a
-    yet written, under a display of its own (2026-10-16,
+    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
@@ -259,20 +212,14 @@ are known.
  opening the database, also while it waits on a busy one. `read` counts the
  records, then reads them against that count. `group` counts the directories it
  groups, and `write` the groups it writes. A display's rate names what its
-  phase counts:
+  phase counts, such as records or groups. stdout and the summary line are
-    - files;
+  unchanged. When stdout and stderr are the same file, as one terminal is, no
-    - records;
+  line of stdout shares a line with the display. When they are not, the display
-    - directories;
+  keeps being drawn while stdout waits on a slow reader (2026-10-16,
-    - groups.
+  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`. It runs from the moment the phase starts and shows:
  shows:
    - the progress;
    - the elapsed time;
    - the ETA, the time remaining.
@@ -297,8 +244,8 @@ are known.
  "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 copied again from `sneak/prompts` `next`
-  `next` at `e3f79c4`:
+  at `e3f79c4`:
    - `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
@@ -312,7 +259,7 @@ are known.
      gone, and the build 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.
+    - a stray editor-settings file is deleted.
    Since https://git.eeqj.de/sneak/sfdupes/issues/109 two steps come before
    `ARG CACHEBUST`:
@@ -323,11 +270,12 @@ are known.
    code still runs on every build (2026-10-15,
    https://git.eeqj.de/sneak/sfdupes/issues/95)
- With `-x`, an operand under another operand is no longer dropped when a
+- With `-x`, an operand under another operand is no longer dropped when the
-  directory between the two, the inner one included, is on a different
+  outer operand's walk cannot reach it. That is the case when a directory
-  filesystem than the outer one. The inner operand is then walked on its own.
+  between the two operands, the inner one included, is on a different filesystem
-  For a regular-file operand the check starts at its directory. The records of
+  than the outer one. The inner operand is then walked on its own. For a
-  files gone from below it are deleted (2026-10-14,
+  regular-file operand the directories checked start at its directory. The
  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
@@ -335,8 +283,8 @@ are known.
  census (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,
@@ -373,8 +321,8 @@ are known.
  `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
-  Gitea workflow checks it. All Markdown was reformatted (2026-10-04,
+  checks 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
@@ -389,7 +337,7 @@ are known.
    (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/16)
- `.golangci.yml` was replaced with the current canonical copy, which uses
+- `.golangci.yml` 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)
@@ -408,8 +356,8 @@ 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,
@@ -479,8 +427,8 @@ are known.
  `dev`. `.dockerignore` sends `.git` without `.git/config`. The build stage
  stamps the `VERSION` build argument, else `git describe --tags --always`. It
  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`),
+  `unknown`. CI checks out the full history (`fetch-depth: 0`), so it stamps the
-  so it stamps the same value as `make build` (2026-10-02, branch `next`,
+  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
@@ -490,18 +438,18 @@ are known.
  phase. The content phase ran after the update phase. It read a file for
  `content` only when its size, `head` and `tail` matched another record's, from
  this scan or an earlier one. `content` was the whole file below 50 MiB, and
-  gigabyte-spaced 1 MiB samples at or above. It never read a file gone or
+  gigabyte-spaced 1 MiB samples at or above. A file gone or changed since its
-  changed since its record was written. `report` and `trees` left out any record
+  record was written was never read. `report` and `trees` left out any record
  without a `content` hash. The `content` column is part of the version 1
  schema. Superseded by https://git.eeqj.de/sneak/sfdupes/issues/132
  (2026-09-22, branch `next`, 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
@@ -524,9 +472,9 @@ are known.
 - 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 from an empty cache, mostly in a `chown -R` of the module cache, filed
-  filed as https://git.eeqj.de/sneak/sfdupes/issues/43. Since
+  as 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`
  phases are the gates (2026-08-09, branch `dockerfile-bootstrap`,
@@ -586,18 +534,17 @@ are known.
    - the whole database layer.
    The walk pool gets the same treatment, plus a `ctx.Err()` guard after the
-    walk. A cancelled walk yields a partial size census, and every file that it
+    walk. A cancelled walk yields a partial size census, and every file it never
-    never reached looks vanished to the update phase. That phase's own `BeginTx`
+    reached looks vanished to the update phase. That phase's own `BeginTx` also
-    also fails on the cancelled context before deleting anything. The guard is
+    fails on the cancelled context before deleting anything. The guard is still
-    still the barrier once an interrupted scan may commit what it has. Tests
+    the barrier once an interrupted scan may commit what it has. Tests drive
-    drive `run(scan)` against a database whose insert trigger aborts. They
+    `run(scan)` against a database whose insert trigger aborts. They assert that
-    assert that the scan fails instead of hanging, and that the goroutine count
+    the scan fails instead of hanging, and that the goroutine count returns to
-    returns to its pre-scan baseline. Other tests cancel a scan part-way through
+    its pre-scan baseline. Other tests cancel a scan part-way through the walk,
-    the walk, deterministically, by counting the scan's own checks of
+    deterministically, by counting the scan's own checks of `ctx.Done()`. They
-    `ctx.Done()`. They assert that it stops at the guard with every record
+    assert that it stops at the guard with every record intact. It then holds a
-    intact. It then holds a partial size census and a still-populated record
+    partial size census and a still-populated record index. Direct tests cover
-    index. Direct tests cover the remaining cancellation branches of both pools.
+    the remaining cancellation branches of both pools. They test:
    They test:
    - `sendEvent`;
    - the walk workers;
    - `dispatchDirs`;
@@ -627,7 +574,7 @@ are known.
    (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
+- `golangci-lint` 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
@@ -640,7 +587,7 @@ are known.
    No new lint findings surfaced (2026-08-09, branch `golangci-v2.12.2`,
    https://git.eeqj.de/sneak/sfdupes/issues/3)
- `Makefile` targets were converted to scripts-to-rule-them-all `script/`
+- `Makefile` targets converted to scripts-to-rule-them-all `script/`
  entrypoints, like the other managed repos. All 12 entrypoints exist:
    - `bootstrap`, `setup` and `projectname`;
    - `test`, `lint`, `fmt`, `fmt-check` and `check`;
@@ -653,15 +600,15 @@ are known.
  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 the
-  scan. So the totals and ETAs cover the whole scan. The per-operand walk, hash
+  totals and ETAs cover the whole scan. The per-operand walk, hash and update
-  and update cycles and their stderr announcements are gone. The update pass
+  cycles and their stderr announcements are gone. The update pass writes in
-  writes in batches, each in its own transaction. The filesystem is
+  batches, each in its own transaction. The filesystem is authoritative and the
-  authoritative and the database follows it, so one scan's changes need not land
+  database follows it, so one scan's changes need not land all at once
-  all at once (2026-07-24, branch `scan-wide-phases`)
+  (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:
    - walk;
    - stat;
@@ -677,32 +624,31 @@ are known.
  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. One ZFS server took 4 hours for 22 million
-  million files. It is now a walk by a pool of per-directory workers that
+  files. It is now a walk by a pool of per-directory workers that records size
-  records size and mtime as it goes. That folds away the separate stat pass and
+  and mtime as it goes. That folds away the separate stat pass and halves the
-  halves the metadata reads. Each `PATH` operand commits in its own transaction,
+  metadata reads. Each `PATH` operand commits in its own transaction, so an
-  so an interrupted scan keeps completed operands (2026-07-24, branch
+  interrupted scan 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 an SQLite database that survives
-  survives between runs, with the absolute path as each record's key. The driver
+  between runs, with the absolute path as each record's key. The driver is
-  is `modernc.org/sqlite`, pure Go, so cgo stays disabled. A rescan hashes only
+  `modernc.org/sqlite`, pure Go, so cgo stays disabled. A rescan hashes only new
-  new or changed files, by mtime and size. It deletes the records of files
+  or changed files, by mtime and size. It deletes the records of files vanished
-  vanished from under the scanned operands and leaves records outside them
+  from under the scanned operands and leaves records outside them untouched. So
-  untouched. So `scan` can run daily from `cron`. `report` and `trees` read the
+  `scan` can run daily from `cron`. `report` and `trees` read the database, with
-  database, with no positional arguments, instead of a scan stream. The database
+  no positional 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`, and `SFDUPES_DATABASE` overrides that. 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` and the tags pushed (2026-07-23)
- The `scan` command line was reworked. Required `PATH...` operands, parsed by
+- `scan` command-line rework. Required `PATH...` operands, parsed by cobra,
-  cobra, replace the `/srv` `-root` default. The new `-x`, `--one-file-system`
+  replace the `/srv` `-root` default. The new `-x`, `--one-file-system` flag
-  flag follows the GNU convention and stops at filesystem boundaries, which the
+  follows the GNU convention and stops at filesystem boundaries, which the walk
-  walk crosses by default (2026-07-23, branch `scan-required-paths`)
+  crosses by default (2026-07-23, branch `scan-required-paths`)
 - The repo was brought into compliance with `REPO_POLICIES.md` (the version of
  2026-07-06), the existing repo checklist and the Go styleguide. The audit of
@@ -714,8 +660,8 @@ are known.
    - `LICENSE` and the README License section. MIT was assumed from house
      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, so
-      `make lint` is clean;
+      that `make lint` is clean;
    - the `Makefile` targets the policy requires:
        - `test` and `lint`;
        - `fmt` and `fmt-check`;
@@ -745,11 +691,10 @@ are known.
    The code was already `gofmt`-clean, so no standalone formatting commit was
    needed (2026-07-23, branch `repo-policy-compliance`)
- `git init` was run, with a README-only first commit. The code baseline was
+- `git init` with a README-only first commit; the code baseline committed on
-  committed on `main` (2026-07-22)
+  `main` (2026-07-22)
- The `scan`, `report` and `trees` subcommands were implemented (pre-git
+- `scan`, `report` and `trees` subcommands implemented (pre-git history)
  history)
 # Future Steps
@@ -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
 `
@@ -146,44 +100,33 @@ var errHashSize = errors.New("hash is not 32 bytes")
 // databasePath resolves the database location: SFDUPES_DATABASE when
 // set and non-empty, the compiled-in default otherwise. It returns the
-// path, made absolute by absolutePath, and where the path came from,
+// path, with the working directory, its symlinks resolved, put in front
-// "default" or "from SFDUPES_DATABASE", for the line each subcommand
+// of it when it is relative, and where the path came from, "default" or
-// prints first on stderr.
+// "from SFDUPES_DATABASE", for the line each subcommand prints first on
 // stderr.
 func databasePath() (string, string, error) {
 	path, source := defaultDatabasePath, "default"
 	if p := os.Getenv(databaseEnv); p != "" {
 		path, source = p, "from "+databaseEnv
 	}
-	abs, err := absolutePath(path)
+	if filepath.IsAbs(path) {
 		return path, source, nil
 	}
 	// The working directory as the kernel reports it, with no symlink
 	// in it, as README "Database" says. os.Getwd may return PWD
 	// instead, which can name it through a symlink.
 	wd, err := unix.Getwd()
 	if err != nil {
 		return "", "", fmt.Errorf("resolve database path %s: %w", path, err)
 	}
-	return abs, source, nil
+	// Not filepath.Abs or filepath.Join: they clean the path, which
-}
+	// drops each ".." together with the directory name before it. When
-
+	// that directory is a symlink, the cleaned path names another file.
 // absolutePath returns path unchanged when it is absolute, and
 // otherwise the working directory, a "/" and path. The working
 // directory is the one the kernel reports, with no symlink in it;
 // os.Getwd may return PWD instead, which can name it through a symlink.
 // The result is not cleaned, as filepath.Abs and filepath.Join would
 // clean it. Cleaning drops each ".." together with the directory name
 // before it. When that name is a symlink, the cleaned path names
 // another file than the one the system reaches by following the symlink
 // first.
 func absolutePath(path string) (string, error) {
 	if filepath.IsAbs(path) {
 		return path, nil
 	}
 	wd, err := unix.Getwd()
 	if err != nil {
 		return "", err
 	}
 	// The working directory ends in "/" only when it is the root.
-	return strings.TrimSuffix(wd, "/") + "/" + path, nil
+	return strings.TrimSuffix(wd, "/") + "/" + path, source, nil
 }
 // createDatabaseDirectory creates the directory the database at path
@@ -207,14 +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
@@ -488,14 +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,
 		totalsAfterInsertSQL, totalsAfterDeleteSQL, totalsAfterUpdateSQL,
 	} {
 		_, err = tx.ExecContext(ctx, stmt)
 	if err != nil {
 		return fmt.Errorf("create schema: %w", err)
 	}
 	_, err = tx.ExecContext(ctx, createIndexSQL)
 	if err != nil {
 		return fmt.Errorf("create schema: %w", err)
 	}
 	_, err = tx.ExecContext(ctx,
@@ -542,7 +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)
 	}
@@ -550,8 +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)
 	}
@@ -565,8 +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)
 		}
@@ -601,11 +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 {
@@ -620,7 +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)
 	}
@@ -686,7 +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)
 	}
@@ -694,10 +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
@@ -740,15 +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)
 	}
@@ -758,18 +696,15 @@ func loadFileMeta(ctx context.Context, db *sql.DB,
 	for rows.Next() {
 		var (
 			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()
@@ -787,21 +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
 		}
@@ -810,26 +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 {
@@ -843,11 +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
@@ -873,7 +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 {
@@ -886,31 +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()
@@ -1,37 +0,0 @@
 package main
 import (
 	"context"
 	"fmt"
 	"io"
 	"os"
 	"runtime"
 )
 // runDwim implements the dwim subcommand: it runs what "sfdupes scan
 // root" runs with no flags, then what "sfdupes trees" runs, and ends
 // with a line on stderr saying how to print the report again. The dwim
 // command passes "/" as root. It catches SIGINT and SIGTERM as scan
 // does, but only during the scan. An error from the scan, an interrupt
 // included, ends it before the report. During the report, a signal
 // ends it at once, as it ends trees.
 func runDwim(ctx context.Context, root string, stdout io.Writer) error {
 	scanCtx, stop := interruptContext(ctx)
 	err := runScan(scanCtx, []string{root}, runtime.NumCPU(), false, false)
 	stop()
 	if err != nil {
 		return err
 	}
 	err = runTrees(ctx, stdout)
 	if err != nil {
 		return err
 	}
 	fmt.Fprintln(os.Stderr,
 		`dwim: run "sfdupes trees" to print this report again`)
 	return nil
 }
@@ -1,83 +0,0 @@
 package main
 import (
 	"bytes"
 	"path/filepath"
 	"strings"
 	"testing"
 )
 func TestRunDwimPrintsLargestTreesFirst(t *testing.T) {
 	// dwim scans its root, then prints the trees report, the larger of
 	// two duplicate-tree pairs first, and ends by saying how to print
 	// the report again.
 	t.Setenv(databaseEnv, testDBPath(t))
 	root := realTempDir(t)
 	small := []string{
 		filepath.Dir(writeFile(t, root, "a1/f.bin", pattern(1, 300))),
 		filepath.Dir(writeFile(t, root, "a2/f.bin", pattern(1, 300))),
 	}
 	large := []string{
 		filepath.Dir(writeFile(t, root, "b1/f.bin", pattern(2, 5000))),
 		filepath.Dir(writeFile(t, root, "b2/f.bin", pattern(2, 5000))),
 	}
 	var stdout bytes.Buffer
 	stderr := captureStderr(t)
 	err := runDwim(t.Context(), root, &stdout)
 	if err != nil {
 		t.Fatalf("runDwim: %v; stderr: %s", err, stderr())
 	}
 	lines := strings.Split(strings.TrimSuffix(stdout.String(), "\n"), "\n")
 	if len(lines) != 3 {
 		t.Fatalf("stdout = %q, want a header and two groups",
 			stdout.String())
 	}
 	wantFirst := large[0] + "\t" + large[1] + "\t1\t5000\t"
 	if !strings.HasPrefix(lines[1], wantFirst) {
 		t.Errorf("first group = %q, want it to start %q", lines[1], wantFirst)
 	}
 	wantSecond := small[0] + "\t" + small[1] + "\t1\t300\t"
 	if !strings.HasPrefix(lines[2], wantSecond) {
 		t.Errorf("second group = %q, want it to start %q",
 			lines[2], wantSecond)
 	}
 	last := "\ndwim: run \"sfdupes trees\" to print this report again\n"
 	if got := stderr(); !strings.HasSuffix(got, last) {
 		t.Errorf("stderr = %q, want it to end %q", got, last)
 	}
 }
 func TestRunDwimScanErrorPrintsNoReport(t *testing.T) {
 	// A fatal scan error ends dwim before the report: a root that does
 	// not exist fails the scan as it fails scan itself.
 	t.Setenv(databaseEnv, testDBPath(t))
 	missing := filepath.Join(realTempDir(t), "missing")
 	var stdout bytes.Buffer
 	stderr := captureStderr(t)
 	err := runDwim(t.Context(), missing, &stdout)
 	if err == nil {
 		t.Fatal("runDwim on a missing root: error = nil, want it fatal")
 	}
 	if got := stdout.String(); got != "" {
 		t.Errorf("stdout = %q, want no report", got)
 	}
 	if got := stderr(); strings.Contains(got, "trees:") ||
 		strings.Contains(got, "dwim:") {
 		t.Errorf("stderr = %q, want nothing from trees or dwim", got)
 	}
 }
@@ -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: {
@@ -286,7 +284,7 @@ func TestRunScanTempDirOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
-	dir := realTempDir(t)
+	dir := t.TempDir()
 	if !underAnyRoot(dir, defaultExcludes(runtime.GOOS)) {
 		t.Skip(dir + " is not inside a default exclude")
 	}
@@ -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,
@@ -14,7 +14,6 @@
 //	sfdupes report > dupes.tsv
 //	sfdupes trees > dupetrees.tsv
 //	sfdupes info
 //	sfdupes dwim
 //	sfdupes --version
 //
 // See README.md for the complete specification.
@@ -46,7 +45,6 @@ const (
 	cmdReport = "report"
 	cmdTrees  = "trees"
 	cmdInfo   = "info"
 	cmdDwim   = "dwim"
 )
 // errNoSubcommand is returned by the root command when it is invoked
@@ -98,8 +96,8 @@ func main() {
 // exit code. It is the program's single exit point: the subcommands
 // return their errors instead of exiting, so every deferred cleanup —
 // above all closing the database, which checkpoints the SQLite WAL —
-// runs before the process ends. The report, trees, info and dwim
+// runs before the process ends. The report, trees and info subcommands
-// subcommands write their data to stdout.
+// write their data to stdout.
 func run(args []string, stdout, stderr io.Writer) int {
 	// A nil slice makes cobra fall back to os.Args, which would let a
 	// test binary's own flags reach the command tree.
@@ -203,16 +201,7 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 		}),
 	}
-	dwimCmd := &cobra.Command{
+	root.AddCommand(newScanCommand(), reportCmd, treesCmd, infoCmd)
 		Use:   cmdDwim,
 		Short: "Scan / with the default excludes, then print the duplicate-tree report",
 		Args:  cobra.NoArgs,
 		RunE: runE(func(ctx context.Context, _ []string) error {
 			return runDwim(ctx, "/", stdout)
 		}),
 	}
 	root.AddCommand(newScanCommand(), reportCmd, treesCmd, infoCmd, dwimCmd)
 	return root
 }
@@ -14,8 +14,6 @@ import (
 	"strconv"
 	"strings"
 	"testing"
 	"golang.org/x/sys/unix"
 )
 // usageMarker is the first line of cobra's usage text, which a usage
@@ -182,9 +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()
@@ -267,9 +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())
 			}
@@ -396,7 +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
@@ -622,7 +619,6 @@ func TestRunUsageErrors(t *testing.T) {
 		"report with args":   {[]string{cmdReport, "x"}, usageMarker},
 		"trees with args":    {[]string{cmdTrees, "x"}, usageMarker},
 		"info with args":     {[]string{cmdInfo, "x"}, usageMarker},
 		"dwim with args":     {[]string{cmdDwim, "x"}, usageMarker},
 		"unknown flag":       {[]string{cmdScan, "--nope", "/"}, usageMarker},
 		"unknown subcommand": {[]string{"nope"}, "unknown command"},
 	}
@@ -652,7 +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) {
@@ -690,8 +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 {
@@ -717,8 +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"} {
@@ -777,8 +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)
@@ -800,7 +796,7 @@ func TestRunVersionWriteFailureIsFatal(t *testing.T) {
 func scanFixture(t *testing.T) []string {
 	t.Helper()
-	dir := realTempDir(t)
+	dir := t.TempDir()
 	dupes := []string{
 		writeFile(t, dir, "one/a.bin", pattern(1, 300)),
@@ -821,23 +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 {
@@ -870,7 +849,7 @@ func TestRunScanSucceedsDespiteWarnings(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
-	dir := realTempDir(t)
+	dir := t.TempDir()
 	writeFile(t, dir, "a.bin", pattern(1, 300))
 	// Same size as a.bin, so the scan reads it, and the read fails.
@@ -898,292 +877,75 @@ func TestRunScanSucceedsDespiteWarnings(t *testing.T) {
 	assertNoSidecars(t, path)
 }
-// realTempDir returns a new temporary directory by its real path, so
+func TestRunScanSkipsSymlinkOperand(t *testing.T) {
 // tests hold where the temporary directory is reached through a
 // symlink.
 func realTempDir(t *testing.T) string {
 	t.Helper()
 	dir, err := filepath.EvalSymlinks(t.TempDir())
 	if err != nil {
 		t.Fatal(err)
 	}
 	return dir
 }
 // symlink creates link pointing at target.
 func symlink(t *testing.T, target, link string) {
 	t.Helper()
 	err := os.Symlink(target, link)
 	if err != nil {
 		t.Fatal(err)
 	}
 }
 // TestRunScanFollowsSymlinkOperand scans link, a symlink to target.
 // The operand is scanned at its real path, and its file is recorded
 // there.
 func TestRunScanFollowsSymlinkOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
-	dir := realTempDir(t)
+	dir := t.TempDir()
-	f := writeFile(t, dir, "target/sub/f", pattern(1, 10))
+	writeFile(t, dir, "target/sub/f", pattern(1, 10))
 	link := filepath.Join(dir, "link")
 	symlink(t, filepath.Join(dir, "target"), link)
-	stderr := scanOK(t, link)
+	err := os.Symlink(filepath.Join(dir, "target"), link)
-
+	if err != nil {
-	summary := "scan: 1 files seen (1 added, 0 updated, 0 removed, " +
+		t.Fatal(err)
 		"0 unchanged), 0 skipped\n"
 	if !strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q", stderr, summary)
 	}
-	if got := storedPaths(t, path); !slices.Equal(got, []string{f}) {
+	// Scanning a directory through the symlink stores a record beneath
-		t.Errorf("records = %q, want %q", got, []string{f})
+	// the symlink's own path for a file beneath its target.
-	}
+	scanOK(t, filepath.Join(link, "sub"))
 	assertOperandSkipped(t, path, link, "symlink",
 		filepath.Join(link, "sub", "f"))
 }
 // TestRunScanWalksOperandUnderSymlinkOperand scans link and link/sub,
 // with link a symlink to target. Both resolve under target, so
 // target/sub is walked once, as part of target.
 func TestRunScanWalksOperandUnderSymlinkOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
-	dir := realTempDir(t)
+	dir := t.TempDir()
-	f := writeFile(t, dir, "target/sub/f", pattern(1, 10))
+	writeFile(t, dir, "target/sub/f", pattern(1, 10))
 	link := filepath.Join(dir, "link")
 	symlink(t, filepath.Join(dir, "target"), link)
-	stderr := scanOK(t, link, filepath.Join(link, "sub"))
+	err := os.Symlink(filepath.Join(dir, "target"), link)
 	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)
 	}
 	if got := storedPaths(t, path); !slices.Equal(got, []string{f}) {
 		t.Errorf("records = %q, want %q", got, []string{f})
 	}
 }
 // TestRunScanWalksSymlinkedOperandBelowOperand is the case of
 // https://git.eeqj.de/sneak/sfdupes/issues/144: scan dir dir/link/sub,
 // with dir/link a symlink to a directory outside dir. The walk of dir
 // does not follow link, so dir/link/sub is walked on its own at its
 // real path, and the record an earlier scan stored there survives.
 func TestRunScanWalksSymlinkedOperandBelowOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := realTempDir(t)
 	a := writeFile(t, dir, "a", pattern(1, 10))
 	outside := realTempDir(t)
 	f := writeFile(t, outside, "sub/f", pattern(2, 10))
 	symlink(t, outside, filepath.Join(dir, "link"))
 	scanOK(t, filepath.Join(outside, "sub"))
 	stderr := scanOK(t, dir, filepath.Join(dir, "link", "sub"))
 	summary := "scan: 2 files seen (1 added, 0 updated, 0 removed, " +
 		"1 unchanged), 0 skipped\n"
 	if !strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q", stderr, summary)
 	}
 	want := []string{a, f}
 	slices.Sort(want)
 	if got := storedPaths(t, path); !slices.Equal(got, want) {
 		t.Errorf("records = %q, want %q", got, want)
 	}
 }
 // TestRunScanDropsSymlinkOperandInsideOperand scans dir and link, with
 // link, outside dir, a symlink to dir/real. link resolves inside dir,
 // so it is dropped as covered by dir, and its file is recorded once.
 func TestRunScanDropsSymlinkOperandInsideOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := realTempDir(t)
 	f := writeFile(t, dir, "real/f", pattern(1, 10))
 	link := filepath.Join(realTempDir(t), "link")
 	symlink(t, filepath.Join(dir, "real"), link)
 	stderr := scanOK(t, dir, link)
 	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)
 	}
 	if got := storedPaths(t, path); !slices.Equal(got, []string{f}) {
 		t.Errorf("records = %q, want %q", got, []string{f})
 	}
 }
 // TestRunScanDanglingSymlinkOperandIsFatal scans a valid directory and
 // a symlink whose target does not exist. The scan fails with exit 1 and
 // an error naming the symlink as given, before it walks anything, so no
 // database is created.
 func TestRunScanDanglingSymlinkOperandIsFatal(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := realTempDir(t)
 	writeFile(t, dir, "f", pattern(1, 10))
 	dangling := filepath.Join(realTempDir(t), "dangling")
 	symlink(t, filepath.Join(dir, "missing"), dangling)
 	stdout := captureStdout(t)
 	var stderr bytes.Buffer
 	code := run([]string{cmdScan, dir, dangling}, os.Stdout, &stderr)
 	if code != exitFatal {
 		t.Errorf("run(scan %s %s) = %d, want %d", dir, dangling, code,
 			exitFatal)
 	}
 	assertFatalOutput(t, stderr.String(), stdout())
 	want := "sfdupes: resolve " + dangling + ": "
 	if !strings.Contains(stderr.String(), want) {
 		t.Errorf("stderr = %q, want %q", stderr.String(), want)
 	}
 	_, err := os.Stat(path)
 	if !errors.Is(err, fs.ErrNotExist) {
 		t.Errorf("database: stat error %v, want it missing", err)
 	}
 }
 // TestRunScanFromSymlinkedWorkingDirectoryRecordsRealPath runs scan .
 // after a cd through home/proj, a symlink to data/proj. The file is
 // recorded under data/proj, its real path.
 func TestRunScanFromSymlinkedWorkingDirectoryRecordsRealPath(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := realTempDir(t)
 	f := writeFile(t, dir, "data/proj/f", pattern(1, 10))
 	err := os.Mkdir(filepath.Join(dir, "home"), 0o750)
 	if err != nil {
 		t.Fatal(err)
 	}
-	symlink(t, filepath.Join(dir, "data", "proj"),
+	// link is dropped as a symlink, but link/sub must still be scanned,
-		filepath.Join(dir, "home", "proj"))
+	// not dropped as lying under link.
 	scanOK(t, link, filepath.Join(link, "sub"))
-	// t.Chdir also sets PWD to the path through the symlink, as a
+	db, err := openDB(path, reportParams)
 	// shell does after cd.
 	t.Chdir(filepath.Join(dir, "home", "proj"))
 	scanOK(t, ".")
 	if got := storedPaths(t, path); !slices.Equal(got, []string{f}) {
 		t.Errorf("records = %q, want %q", got, []string{f})
 	}
 }
 // TestRunScanFollowsSymlinkBeforeDotDot scans a path with a ".." after
 // home/proj, a symlink to data/proj: home/proj/.. from dir, and .. after
 // a cd through home/proj. As with realpath, the ".." counts from
 // data/proj, so data is scanned and home is not.
 func TestRunScanFollowsSymlinkBeforeDotDot(t *testing.T) {
 	for _, tc := range []struct{ wd, operand string }{
 		{"", "home/proj/.."},
 		{"home/proj", ".."},
 	} {
 		t.Run(tc.operand, func(t *testing.T) {
 			path := testDBPath(t)
 			t.Setenv(databaseEnv, path)
 			dir := realTempDir(t)
 			f := writeFile(t, dir, "data/proj/f", pattern(1, 10))
 			g := writeFile(t, dir, "data/g", pattern(2, 10))
 			writeFile(t, dir, "home/h", pattern(3, 10))
 			symlink(t, filepath.Join(dir, "data", "proj"),
 				filepath.Join(dir, "home", "proj"))
 			// t.Chdir also sets PWD to the path given, as a shell does
 			// after cd.
 			t.Chdir(filepath.Join(dir, tc.wd))
 			scanOK(t, tc.operand)
 			want := []string{f, g}
 			slices.Sort(want)
 			if got := storedPaths(t, path); !slices.Equal(got, want) {
 				t.Errorf("records = %q, want %q", got, want)
 			}
 		})
 	}
 }
 // TestRunScanSkipsSymlinkToFIFOOperand scans link, a symlink to a FIFO.
 // The scan warns about the FIFO by its real path, counts it as skipped,
 // and exits 0.
 func TestRunScanSkipsSymlinkToFIFOOperand(t *testing.T) {
 	t.Setenv(databaseEnv, testDBPath(t))
 	dir := realTempDir(t)
 	fifo := filepath.Join(dir, "fifo")
 	err := unix.Mkfifo(fifo, 0o600)
 	if err != nil {
 		t.Fatal(err)
 	}
-	link := filepath.Join(dir, "link")
+	t.Cleanup(func() { _ = db.Close() })
 	symlink(t, fifo, link)
-	stderr := scanOK(t, link)
+	recordByPath(t, dbRecords(t, db), filepath.Join(link, "sub", "f"))
 	warning := "walk " + fifo + ": skipping FIFO operand\n"
 	if !strings.Contains(stderr, warning) {
 		t.Errorf("stderr = %q, want %q", stderr, warning)
 	}
 	summary := "scan: 0 files seen (0 added, 0 updated, 0 removed, " +
 		"0 unchanged), 1 skipped\n"
 	if !strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q", stderr, summary)
 	}
 }
 func TestRunScanSkipsZFSOperand(t *testing.T) {
-	zfs := filepath.Join(realTempDir(t), ".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,
 ) {
@@ -1212,107 +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 := realTempDir(t)
 	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 its real path, counted as skipped, and not walked.
 func TestRunScanSkipsOperandThroughSymlinkIntoZFS(t *testing.T) {
 	t.Setenv(databaseEnv, testDBPath(t))
 	dir := realTempDir(t)
 	writeFile(t, dir, "pool/.zfs/snapshot/daily/f", pattern(1, 10))
 	snaps := filepath.Join(dir, "snaps")
 	symlink(t, filepath.Join(dir, "pool", ".zfs", "snapshot"), snaps)
 	stderr := scanOK(t, filepath.Join(snaps, "daily"))
 	daily := filepath.Join(dir, "pool", ".zfs", "snapshot", "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 pool/data. The operand is scanned as usual, and its file
 // is recorded by its real path.
 func TestRunScanWalksOperandThroughSymlink(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := realTempDir(t)
 	f := writeFile(t, dir, "pool/data/daily/f", pattern(1, 10))
 	data := filepath.Join(dir, "data")
 	symlink(t, filepath.Join(dir, "pool", "data"), data)
 	stderr := scanOK(t, filepath.Join(data, "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)
 	}
 	if got := storedPaths(t, path); !slices.Equal(got, []string{f}) {
 		t.Errorf("records = %q, want %q", got, []string{f})
 	}
 }
 func TestRunReportSucceeds(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
@@ -1367,9 +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)
 	}
@@ -1403,10 +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 {
@@ -1441,11 +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)
 	}
@@ -1466,7 +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
@@ -1511,8 +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)
@@ -1571,7 +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.
@@ -1676,8 +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
@@ -21,11 +21,9 @@ 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
 	diskSize int64
 	mtime   time.Time
 	head    [sha256.Size]byte
 	tail    [sha256.Size]byte
@@ -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"},
 	}
 }
@@ -52,25 +52,22 @@ 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
 	size  int64
 	diskSize int64
 	mtime time.Time
 	dev   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
 	diskSize int64
 	mtime time.Time
 }
@@ -209,30 +206,29 @@ func interrupted(walked int) error {
 	return errInterrupted
 }
-// resolveRoots converts each PATH operand to its real path: absolute,
+// resolveRoots converts each PATH operand to an absolute, lexically
-// with every symlink in it followed. Database records are keyed by
+// cleaned path (symlinks are not resolved) and verifies that it
-// that path, so scan results depend neither on the working directory
+// exists. Database records are keyed by absolute path, so scan results
-// nor on the symlinks an operand was given through. An operand that
+// must not depend on the working directory.
 // cannot be resolved, because it or a symlink's target does not exist
 // or cannot be read, is a fatal error before any scanning.
 func resolveRoots(roots []string) ([]string, error) {
-	resolved := make([]string, 0, len(roots))
+	abs := make([]string, 0, len(roots))
 	for _, root := range roots {
-		a, err := absolutePath(root)
+		a, err := filepath.Abs(root)
 		if err != nil {
 			return nil, fmt.Errorf("resolve %s: %w", root, err)
 		}
-		r, err := filepath.EvalSymlinks(a)
+		// A nonexistent operand is a fatal error before any scanning.
 		_, err = os.Lstat(a)
 		if err != nil {
-			return nil, fmt.Errorf("resolve %s: %w", root, err)
+			return nil, err
 		}
-		resolved = append(resolved, r)
+		abs = append(abs, a)
 	}
-	return resolved, nil
+	return abs, nil
 }
 // pruneRoots drops operands already covered by another operand:
@@ -346,7 +342,6 @@ type scanState struct {
 	db       *sql.DB
 	existing map[string]fileMeta
 	toHash   []fileRec // new and changed files: must be read
 	diskSizes []fileRec // unchanged files whose disk_size changed
 	batch    []scanRec
 	st       scanStats
 }
@@ -388,8 +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)
@@ -417,17 +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. The operands are real paths from resolveRoots,
+// about, counted as skipped, and dropped. A dropped operand is no
-// so these checks apply to what a symlink operand points at. Every
+// longer a root, so the records stored beneath it are treated as if it
-// other operand is warned about, counted as skipped, and dropped. A
+// had not been given: those under no other root count as outside the
-// dropped operand is no longer a root, so the records stored beneath it
+// roots and are not deleted as unverified. An operand on a filesystem
-// are treated as if it had not been given: those under no other root
+// in rules that is not persistent is dropped the same way, with a line
-// count as outside the roots and are not deleted as unverified. An
+// saying so that is not a warning, and is not counted as skipped. An
-// operand on a filesystem in rules that is not persistent is dropped
+// operand that fails lstat here is kept, and the walk warns about it
-// the same way, with a line saying so that is not a warning, and is not
+// unless it no longer exists.
 // counted as skipped. An operand that fails lstat here is kept, and the
 // walk warns about it unless it no longer exists.
 func (s *scanState) walkableRoots(roots []string, rules walkRules) []string {
 	kept := make([]string, 0, len(roots))
@@ -462,8 +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",
@@ -479,24 +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,
 		func(path string, size int64, mtime time.Time) {
 			prog.increment()
 			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.
@@ -554,13 +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
 		// up to seconds after the write.
 		if old.diskSize != ev.rec.diskSize {
 			s.diskSizes = append(s.diskSizes, ev.rec)
 		}
 	}
 	prog.finish()
@@ -710,7 +695,6 @@ func (s *scanState) recordRun(ctx context.Context, r hashResult) error {
 		s.batch = append(s.batch, scanRec{
 			size:    rec.size,
 			diskSize: rec.diskSize,
 			mtime:   rec.mtime,
 			head:    r.head,
 			tail:    r.tail,
@@ -731,7 +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
 	}
@@ -742,10 +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 {
@@ -757,7 +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",
@@ -772,11 +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)
 }
@@ -896,18 +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. resolveRoots has already followed the
+// never followed, including as operands.
 // operand's symlinks, so a symlink here is an operand replaced by one
 // after it was resolved, and is not followed.
 func operandWarning(root string, fi fs.FileInfo) string {
 	// The walk never enters a .zfs directory, so it starts from nothing
 	// inside one either.
 	if slices.Contains(strings.Split(filepath.Dir(root), "/"), ".zfs") {
 		return fmt.Sprintf("walk %s: skipping operand inside a .zfs directory",
 			root)
 	}
 	var kind string
 	switch mode := fi.Mode(); {
@@ -978,7 +947,6 @@ func seedRoot(ctx context.Context, root string, rules walkRules,
 	rec := fileRec{
 		path:  root,
 		size:  fi.Size(),
 		diskSize: diskSizeOfInfo(fi),
 		mtime: fi.ModTime(),
 		dev:   dev,
 		ino:   ino,
@@ -1163,7 +1131,6 @@ func emitFile(ctx context.Context, p string, e fs.DirEntry,
 	rec := fileRec{
 		path:  p,
 		size:  info.Size(),
 		diskSize: diskSizeOfInfo(info),
 		mtime: info.ModTime(),
 		dev:   dev,
 		ino:   ino,
@@ -1258,23 +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.
@@ -42,30 +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 write's
 // blocks only when it commits the write, up to seconds later, and one
 // commit can take the file through several growing sizes. So this value
 // can change at any moment. Neither fsync nor unix.Sync hastens that,
 // but a unix.Sync call often takes long enough that the blocks are
 // counted when it returns. A test that needs the value to change waits
 // for the change. A test that compares it with a scan's disk_size reads
 // it before and after the scan. The rewrite test rescans until the two
 // reads match, then compares exactly. The other two tests fail only on
 // a disk_size outside the two reads.
 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)
@@ -1088,13 +1064,12 @@ 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()
-	dir := realTempDir(t)
+	dir := t.TempDir()
 	one := pattern(10, 2000)
 	f1 := pattern(30, 3000)
 	f2 := pattern(40, 100)
@@ -1253,9 +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) {
@@ -1441,159 +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
 	size := diskSizeOf(t, p)
 	if size == 0 || size >= length {
 		t.Fatalf("the file takes %d bytes on disk, want more than none "+
 			"and fewer than its length %d", size, length)
 	}
 	for _, operand := range []string{filepath.Dir(p), p} {
 		db := openTestDB(t)
 		// ZFS may count the blocks during the scan; see diskSizeOf.
 		before := diskSizeOf(t, p)
 		syncTree(t, db, operand)
 		after := diskSizeOf(t, p)
 		got := recordByPath(t, dbRecords(t, db), p).diskSize
 		if got < before || got > after {
 			t.Errorf("scan of %s: disk_size = %d, want %d to %d",
 				operand, got, before, after)
 		}
 	}
 }
 // 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)
 	recorded := 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)
 	}
 	// Wait for ZFS to count the write; see diskSizeOf.
 	deadline := time.Now().Add(30 * time.Second)
 	for diskSizeOf(t, p) == recorded {
 		if time.Now().After(deadline) {
 			t.Fatalf("the file still takes %d bytes on disk 30 seconds "+
 				"after the write into its hole", recorded)
 		}
 		unix.Sync()
 	}
 	// ZFS may still be counting, so the size may change during a rescan.
 	// Only a rescan with the same size on both sides of it can be compared
 	// exactly. A rescan that keeps the old size still fails, because the
 	// wait made before differ from it.
 	for {
 		before := diskSizeOf(t, p)
 		st := syncTree(t, db, dir)
 		after := diskSizeOf(t, p)
 		if st != (scanStats{walked: 1, updated: 1}) {
 			t.Fatalf("rescan stats = %+v, want 1 updated", st)
 		}
 		if before == after {
 			got := recordByPath(t, dbRecords(t, db), p).diskSize
 			if got != after {
 				t.Errorf("disk_size = %d, want %d", got, after)
 			}
 			return
 		}
 		if time.Now().After(deadline) {
 			t.Fatalf("the size on disk was still changing 30 seconds after "+
 				"the write into its hole: %d, then %d", before, after)
 		}
 		// A later mtime makes the next rescan read the file again.
 		later = later.Add(time.Second)
 		err = os.Chtimes(p, later, later)
 		if err != nil {
 			t.Fatal(err)
 		}
 	}
 }
 // 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
 	// ZFS may count the blocks during the rescan; see diskSizeOf.
 	before := diskSizeOf(t, p)
 	// A file read again would count as updated.
 	st := syncTree(t, db, dir)
 	after := diskSizeOf(t, p)
 	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 got < before || got > after {
 		t.Errorf("disk_size = %d, want %d to %d", got, before, after)
 	}
 }
 // 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
@@ -2310,24 +2132,33 @@ func TestUnderRoot(t *testing.T) {
 }
 // TestRunScanPassesOverDatabase scans a tree that holds the scan's own
-// database, and in one case also a hard link to the database file. The
+// database, reached directly and through a symlinked directory. The
-// walk knows the database's files by device ID and inode number, so it
+// walk passes over the database file, its -wal and -shm files and its
-// passes over the database file, its -wal and -shm files, its .lock
+// .lock file with no line and no count, and the record an earlier scan
-// file and the hard link with no line and no count. The record an
+// left for the .lock file is deleted. A rescan of the unchanged tree
-// earlier scan left for the .lock file is deleted. A rescan of the
+// updates nothing, and report lists none of the database's files.
 // unchanged tree updates nothing, and report lists none of the
 // database's files.
 func TestRunScanPassesOverDatabase(t *testing.T) {
-	for _, viaHardLink := range []bool{false, true} {
+	for _, viaSymlink := range []bool{false, true} {
-		t.Run(fmt.Sprintf("via hard link %v", viaHardLink), func(t *testing.T) {
+		t.Run(fmt.Sprintf("via symlink %v", viaSymlink), func(t *testing.T) {
-			tree := realTempDir(t)
+			base := t.TempDir()
-			hardLink := filepath.Join(tree, "hardlink")
+			tree := filepath.Join(base, "real", "tree")
 			operand := tree
 			writeFile(t, tree, "a", pattern(1, 100))
 			writeFile(t, tree, "b", pattern(1, 100))
 			writeFile(t, tree, "empty1", nil)
 			writeFile(t, tree, "empty2", nil)
 			if viaSymlink {
 				err := os.Symlink(filepath.Join(base, "real"),
 					filepath.Join(base, "link"))
 				if err != nil {
 					t.Fatal(err)
 				}
 				operand = filepath.Join(base, "link", "tree")
 			}
 			dbPath := filepath.Join(tree, "db.sqlite")
 			t.Setenv(databaseEnv, dbPath)
@@ -2337,7 +2168,7 @@ func TestRunScanPassesOverDatabase(t *testing.T) {
 			}
 			err = applyChanges(t.Context(), db, []scanRec{
-				{path: filepath.Join(tree, "db.sqlite.lock")},
+				{path: filepath.Join(operand, "db.sqlite.lock")},
 			}, nil, nil)
 			if err != nil {
 				t.Fatal(err)
@@ -2345,29 +2176,16 @@ func TestRunScanPassesOverDatabase(t *testing.T) {
 			closeScanDatabase(t.Context(), db, dbPath)
-			if viaHardLink {
+			assertScanSummary(t,
 				err = os.Link(dbPath, hardLink)
 				if err != nil {
 					t.Fatal(err)
 				}
 			}
 			stderr := assertScanSummary(t,
 				"4 files seen (4 added, 0 updated, 1 removed, 0 unchanged)",
-				tree)
+				operand)
-			stderr += assertScanSummary(t,
+			assertScanSummary(t,
 				"4 files seen (0 added, 0 updated, 0 removed, 4 unchanged)",
-				tree)
+				operand)
 			if strings.Contains(stderr, hardLink) {
 				t.Errorf("scan stderr = %q, want no line naming %s",
 					stderr, hardLink)
 			}
 			report := runStdout(t, cmdReport)
 			if strings.Contains(report, "db.sqlite") ||
-				strings.Contains(report, hardLink) ||
+				!strings.Contains(report, filepath.Join(operand, "empty2")) {
 				!strings.Contains(report, filepath.Join(tree, "empty2")) {
 				t.Errorf("report = %q, want the empty files and none of "+
 					"the database's files", report)
 			}
@@ -2392,9 +2210,8 @@ func TestRunScanPassesOverDatabaseOperands(t *testing.T) {
 // assertScanSummary scans operands and fails the test unless the
 // summary line gives counts with nothing skipped, and the line naming
-// the database is the only one that names one of its files. It returns
+// the database is the only one that names one of its files.
-// everything the scan printed to stderr.
+func assertScanSummary(t *testing.T, counts string, operands ...string) {
 func assertScanSummary(t *testing.T, counts string, operands ...string) string {
 	t.Helper()
 	stderr := scanOK(t, operands...)
@@ -2408,6 +2225,4 @@ func assertScanSummary(t *testing.T, counts string, operands ...string) string {
 		t.Errorf("scan %q: stderr = %q, want only the line naming the "+
 			"database to name one of its files", operands, stderr)
 	}
 	return stderr
 }
@@ -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)
 	}