Resolve scan operands to their real paths (closes #144)

scan now resolves every operand with its symlinks followed before the
walk, and uses that real path for pruning, walking, records and
warnings. A relative operand is joined to the working directory as the
kernel reports it, so a ".." after a symlink counts from its target, as
with realpath. A symlink operand is scanned at its target instead of
skipped. An operand given through a symlink below another operand, to a
directory outside it, is walked on its own instead of dropped with its
records deleted. An operand that cannot be resolved is a fatal error
naming the operand as given. The walk itself still follows no symlink.

Model: opus-5-5

README.md

@@ -17,13 +17,12 @@ gigabyte. A large file is never read in full. A match between two large files is
 a strong candidate, not proof.
 
 `sfdupes` is meant for multi-terabyte servers, where reading every byte of every
-file takes too long. It has five subcommands. `scan` walks the filesystem and
+file takes too long. It has four subcommands. `scan` walks the filesystem and
 records the files it finds in an SQLite database. SQLite keeps a whole database
 in one file. The database is kept between runs. A rescan reads only new and
 changed files. That makes `scan` cheap enough to run every day from `cron`, the
 system's job scheduler. `report`, `trees` and `info` read the database alone and
-can run at any time. `dwim` scans `/` and then prints the `trees` report, for a
+can run at any time.
-first look at a new machine with one command.
 
 ## Getting Started
 
@@ -248,15 +247,12 @@ In order:
 - `report` prints the file-level duplicate report from the database.
 - `trees` prints the duplicate-tree report from the database.
 - `info` prints the database's details.
-- `dwim` scans `/` with the default excludes, then prints the duplicate-tree
-  report.
 
 ```
 sfdupes scan [--workers N] [-x] [--no-default-excludes] PATH...
 sfdupes report > dupes.tsv
 sfdupes trees > dupetrees.tsv
 sfdupes info
-sfdupes dwim
 sfdupes --version
 sfdupes [command] --help
 ```
@@ -368,10 +364,8 @@ default. An operand may be a directory or a regular file.
 - An operand that repeats another is dropped before the walk. Two operands
   repeat each other when their real paths are the same.
 - An operand under another operand is dropped the same way, unless one of the
-  cases below applies. No path is then walked twice. Whether one operand is
+  cases below applies. This too is judged on real paths. No path is then walked
-  under another is judged on their real paths. With `/srv/link` a symlink to a
+  twice.
-  directory outside `/srv`, `scan /srv /srv/link/sub` walks `sub` on its own,
-  because the real path of `sub` is not under `/srv`.
 - An operand under another is kept, and walked on its own, when the inner
   operand or a directory between the two is one of these:
     - a default exclude (see "Rules for the walk");
@@ -383,6 +377,8 @@ default. An operand may be a directory or a regular file.
     such a directory, so the inner operand is walked on its own.
 
 - No other case keeps an operand under another.
+- With `/srv/link` a symlink to a directory outside `/srv`,
+  `scan /srv /srv/link/sub` walks `sub` on its own, at its real path.
 - An operand that is neither a regular file nor a directory is not scanned. Such
   an operand is, for example, a symlink to a device node. `scan` prints a
   warning naming the real path and what it is. It counts the operand as skipped
@@ -804,33 +800,6 @@ The summary line on stderr gives:
 trees: 14 records read, 1 duplicate tree groups, 1 dupe trees, 3.0 KiB reclaimable
 ```
 
-### `dwim` mode
-
-`dwim`, short for "do what I mean", scans a new machine and reports its
-duplicate trees in one command. It takes no positional arguments and no flags of
-its own. Like `scan`, it should run as root, so that it can read every file.
-
-`dwim` runs what `sfdupes scan /` runs with no flags. The walk skips the default
-excludes and crosses into other filesystems. `--workers` keeps its default. The
-database, its creation and the scan lock are those of `scan`. Then `dwim` runs
-what `sfdupes trees` runs. The largest trees come first.
-
-The report goes to stdout, exactly as `trees` prints it. On stderr comes what
-`scan` prints, then what `trees` prints, then one last line:
-
-```
-dwim: run "sfdupes trees" to print this report again
-```
-
-The database keeps the scan, so `sfdupes trees` prints the same report later,
-even after the terminal is gone.
-
-`SIGINT` or `SIGTERM` stops the scan as it stops `scan` (see "Stopping a scan").
-`dwim` then prints no report and exits 1. A fatal scan error also ends it before
-the report, with the same message and exit code as `scan`. Warnings for skipped
-files do not stop it. `dwim` stops catching signals when the scan ends, so a
-signal during the report ends it at once, as it ends `trees`.
-
 ### `info` mode
 
 `info` takes no positional arguments and prints the database's details on
@@ -871,7 +840,7 @@ scan is writing. `info` writes its lines after the `count` display has ended.
 
 ### Database
 
-All five subcommands work on one SQLite database file.
+All four subcommands work on one SQLite database file.
 
 #### Location
 
@@ -887,8 +856,6 @@ scan: new database /var/lib/sfdupes/db.sqlite (default)
 trees: database /srv/tmp/sfdupes/db.db (from SFDUPES_DATABASE)
 ```
 
-`dwim` prints the `scan` line first, and the `trees` line after the scan.
-
 A relative path is printed with the working directory in front of it. The
 working directory is printed as `pwd -P` prints it, with its symlinks resolved.
 The rest of the path is printed as set, so a `..` in it stays. The line names
@@ -1172,8 +1139,8 @@ showing the count it stopped at.
 ### Error handling and exit codes
 
 - `0`: success, even when files were skipped with warnings.
-- `1`: a fatal error, a `scan` stopped by `SIGINT` or `SIGTERM`, or a `dwim`
+- `1`: a fatal error, or a `scan` stopped by `SIGINT` or `SIGTERM`. A fatal
-  stopped by either during its scan. A fatal error is one of these:
+  error is one of these:
     - an operand that does not exist, or whose real path `scan` cannot find;
     - a list of mounted filesystems that `scan` cannot read;
     - another `scan` holding the lock (see "The scan lock");
@@ -1194,7 +1161,7 @@ showing the count it stopped at.
       `--workers abc`;
     - `scan` with no operand;
     - `--workers` below 1;
-    - `report`, `trees`, `info` or `dwim` with a positional argument.
+    - `report`, `trees` or `info` with a positional argument.
 
 A fatal error is reported on stderr, starting with `sfdupes:`. A failed write to
 stdout, such as a full disk, is reported the same way. Two cases never reach

TODO.md

@@ -29,11 +29,6 @@
 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`

dwim.go

@@ -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
-}

dwim_test.go

@@ -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)
-	}
-}

exclude_test.go

@@ -286,7 +286,7 @@ 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")
 	}

main.go

@@ -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
 }

main_test.go

@@ -622,7 +622,6 @@ 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"},
 	}
@@ -800,7 +799,7 @@ 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)),
@@ -870,7 +869,7 @@ 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.
@@ -922,6 +921,15 @@ func symlink(t *testing.T, target, link string) {
 	}
 }
 
+// assertSummary checks that stderr holds the scan summary line want.
+func assertSummary(t *testing.T, stderr, want string) {
+	t.Helper()
+
+	if !strings.Contains(stderr, want) {
+		t.Errorf("stderr = %q, want %q", stderr, want)
+	}
+}
+
 // TestRunScanFollowsSymlinkOperand scans link, a symlink to target.
 // The operand is scanned at its real path, and its file is recorded
 // there.
@@ -935,13 +943,8 @@ func TestRunScanFollowsSymlinkOperand(t *testing.T) {
 	link := filepath.Join(dir, "link")
 	symlink(t, filepath.Join(dir, "target"), link)
 
-	stderr := scanOK(t, link)
+	assertSummary(t, scanOK(t, link), "scan: 1 files seen (1 added, "+
-
+		"0 updated, 0 removed, 0 unchanged), 0 skipped\n")
-	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})
@@ -961,13 +964,9 @@ func TestRunScanWalksOperandUnderSymlinkOperand(t *testing.T) {
 	link := filepath.Join(dir, "link")
 	symlink(t, filepath.Join(dir, "target"), link)
 
-	stderr := scanOK(t, link, filepath.Join(link, "sub"))
+	assertSummary(t, scanOK(t, link, filepath.Join(link, "sub")),
-
+		"scan: 1 files seen (1 added, 0 updated, 0 removed, "+
-	summary := "scan: 1 files seen (1 added, 0 updated, 0 removed, " +
+			"0 unchanged), 0 skipped\n")
-		"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})
@@ -994,12 +993,8 @@ func TestRunScanWalksSymlinkedOperandBelowOperand(t *testing.T) {
 	scanOK(t, filepath.Join(outside, "sub"))
 
 	stderr := scanOK(t, dir, filepath.Join(dir, "link", "sub"))
-
+	assertSummary(t, stderr, "scan: 2 files seen (1 added, 0 updated, "+
-	summary := "scan: 2 files seen (1 added, 0 updated, 0 removed, " +
+		"0 removed, 1 unchanged), 0 skipped\n")
-		"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)
@@ -1022,13 +1017,8 @@ func TestRunScanDropsSymlinkOperandInsideOperand(t *testing.T) {
 	link := filepath.Join(realTempDir(t), "link")
 	symlink(t, filepath.Join(dir, "real"), link)
 
-	stderr := scanOK(t, dir, link)
+	assertSummary(t, scanOK(t, dir, link), "scan: 1 files seen (1 added, "+
-
+		"0 updated, 0 removed, 0 unchanged), 0 skipped\n")
-	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})
@@ -1161,15 +1151,12 @@ func TestRunScanSkipsSymlinkToFIFOOperand(t *testing.T) {
 		t.Errorf("stderr = %q, want %q", stderr, warning)
 	}
 
-	summary := "scan: 0 files seen (0 added, 0 updated, 0 removed, " +
+	assertSummary(t, stderr, "scan: 0 files seen (0 added, 0 updated, "+
-		"0 unchanged), 1 skipped\n"
+		"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")
+	zfs := filepath.Join(t.TempDir(), ".zfs")
 	f := writeFile(t, zfs, "snapshot/hourly/f", pattern(1, 10))
 
 	// No scan records a file inside a .zfs directory, so the record
@@ -1220,7 +1207,7 @@ func TestRunScanSkipsOperandInsideZFS(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 
-	dir := realTempDir(t)
+	dir := t.TempDir()
 	hourly := filepath.Join(dir, ".zfs", "snapshot", "hourly")
 	writeFile(t, hourly, "f", pattern(1, 10))
 	f := writeFile(t, dir, "f", pattern(2, 10))
@@ -1300,13 +1287,9 @@ func TestRunScanWalksOperandThroughSymlink(t *testing.T) {
 	data := filepath.Join(dir, "data")
 	symlink(t, filepath.Join(dir, "pool", "data"), data)
 
-	stderr := scanOK(t, filepath.Join(data, "daily"))
+	assertSummary(t, scanOK(t, filepath.Join(data, "daily")),
-
+		"scan: 1 files seen (1 added, 0 updated, 0 removed, "+
-	summary := "scan: 1 files seen (1 added, 0 updated, 0 removed, " +
+			"0 unchanged), 0 skipped\n")
-		"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})

scan_test.go

@@ -1094,7 +1094,7 @@ func TestScanOneFilesystemWalksNestedFileOperand(t *testing.T) {
 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)