scan: drop the stray [flags] from the usage line (closes #169)

The scan Use string already names every flag, so cobra no longer appends
its generic [flags]. A test checks the usage line in the help and in the
usage error against the one README.md shows.

Model: opus-5-5

README.md

@@ -665,6 +665,7 @@ Processing:
 - Records are grouped by signature, the four values
   `(size, head, tail, content)`.
 - Every group with two or more paths is a duplicate group.
+- Empty files form no group, because removing one frees nothing.
 - Within a group, paths are sorted in byte order. The first is `first`, and
   every other path is a `dupe`.
 - Groups are ordered by size, largest first, then by `first` path. The output is
@@ -713,7 +714,7 @@ The summary line on stderr gives:
 - the reclaimable bytes, the sum of `size` over all rows.
 
 ```
-report: 14 records read, 5 duplicate groups, 8 dupe files, 10.0 KiB reclaimable
+report: 14 records read, 4 duplicate groups, 7 dupe files, 10.0 KiB reclaimable
 ```
 
 ### `trees` mode
@@ -741,6 +742,9 @@ Processing:
 - `trees` builds the directory tree and computes every directory's digest. It
   then groups the directories by digest. Every group with two or more
   directories is a duplicate-tree group.
+- `trees` leaves out a group whose trees hold 0 bytes, because removing one
+  frees nothing. An empty file still counts toward the digest of a tree that
+  holds other files.
 - `trees` leaves out a group that a group of its members' parents already
   implies. A group is left out when its members' parents are distinct
   directories that all have the same digest. The parents' group, or an
@@ -1139,11 +1143,6 @@ On a terminal:
     ⠹ [3/4] hash: [12345/98765], 92 files/s, elapsed 2m32s, remain 17m44s            12% |█         |
     ```
 
-- During `scan`'s `walk`, the line below the display shows the path of the last
-  file the walk found. Each draw shows the path of that moment, cut short before
-  the terminal's last column. The line is erased when the walk ends, and the
-  next phase is drawn on it.
-
 - No line reaches the terminal's last column. A line too wide for the terminal
   first leaves out its rate, the words of a stalled phase, or what the phase is
   waiting for. It leaves out its bar next. It is cut short at the edge only when
@@ -1387,7 +1386,7 @@ All of the following, run in this directory, must pass:
     head -c 2000 /dev/urandom > "$d/a/unique.bin"     # same size, different content
     printf 'x' > "$d/tiny1"; printf 'x' > "$d/tiny2"  # 1-byte duplicates
     printf 'y' > "$d/tiny3"                           # 1-byte non-duplicate
-    : > "$d/empty1"; : > "$d/empty2"                  # empty duplicates
+    : > "$d/empty1"; : > "$d/empty2"                  # empty files
     # duplicate trees: t1 and t2 are identical; t3 differs by one filename
     mkdir -p "$d/t1/sub" "$d/t2/sub" "$d/t3/sub"
     head -c 3000 /dev/urandom > "$d/t1/f1"
@@ -1412,8 +1411,8 @@ All of the following, run in this directory, must pass:
       is the path that sorts first.
     - `t1/f1`, `t2/f1` and `t3/f1` form one group.
     - `t1/sub/f2`, `t2/sub/f2` and `t3/sub/f2renamed` form one group.
-    - `tiny1` and `tiny2` form a pair, and so do `empty1` and `empty2`.
+    - `tiny1` and `tiny2` form a pair.
-    - `unique.bin` and `tiny3` appear nowhere.
+    - `unique.bin`, `tiny3`, `empty1` and `empty2` appear nowhere.
     - The groups come in order of size, largest first.
 
     `trees` prints exactly one row, `$d/t1` as `first` and `$d/t2` as `dupe`.

TODO.md

@@ -29,11 +29,13 @@
 Newest first. An entry ends with its date and its issue or branch, where those
 are known.
 
-- On a terminal, the line below the `walk` display shows the path of the last
+- The usage line of `scan` no longer ends in `[flags]`. It is the line
-  file the walk found, at each draw. The line is erased when the walk ends, and
+  `README.md` shows under "Subcommands" (2026-11-11,
-  the next phase is drawn on it (2026-11-10,
+  https://git.eeqj.de/sneak/sfdupes/issues/169)
-  https://git.eeqj.de/sneak/sfdupes/issues/160)
+- `report` and `trees` leave out empty files. `report` writes no group of size
-
+  0, and `trees` writes no group whose trees hold 0 bytes. An empty file still
+  counts toward a tree's digest (2026-11-11,
+  https://git.eeqj.de/sneak/sfdupes/issues/178)
 - The Go code moved out of the repository root. `cmd/sfdupes/main.go` is the
   command, and it calls `Main` in the package `internal/sfdupes`. `main.go`
   became `internal/sfdupes/cli.go`. Every other file kept its name. The install

go.mod

@@ -3,7 +3,6 @@ module sneak.berlin/go/sfdupes
 go 1.25.7
 
 require (
-	github.com/rivo/uniseg v0.4.7
 	github.com/schollz/progressbar/v3 v3.19.1
 	github.com/spf13/cobra v1.10.2
 	golang.org/x/sys v0.46.0
@@ -19,6 +18,7 @@ require (
 	github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	modernc.org/libc v1.74.1 // indirect
 	modernc.org/mathutil v1.7.1 // indirect

internal/sfdupes/cli.go

@@ -215,10 +215,13 @@ func newScanCommand() *cobra.Command {
 	short := "Walk trees and synchronize the scan database"
 
 	scanCmd := &cobra.Command{
-		Use:   cmdScan + " [--workers N] [-x] [--no-default-excludes] PATH...",
+		Use: cmdScan + " [--workers N] [-x] [--no-default-excludes] PATH...",
-		Short: short,
+		// The Use line already names every flag, so cobra must not
-		Long:  short + ".\n\n" + defaultExcludesHelp(runtime.GOOS),
+		// append its generic "[flags]" to it.
-		Args:  cobra.MinimumNArgs(1),
+		DisableFlagsInUseLine: true,
+		Short:                 short,
+		Long:                  short + ".\n\n" + defaultExcludesHelp(runtime.GOOS),
+		Args:                  cobra.MinimumNArgs(1),
 		PreRunE: func(cmd *cobra.Command, _ []string) error {
 			return checkScanWorkers(cmd, scanWorkers)
 		},

internal/sfdupes/cli_test.go

@@ -714,6 +714,34 @@ func TestRunHelp(t *testing.T) {
 	}
 }
 
+func TestRunScanUsageLine(t *testing.T) {
+	t.Parallel()
+
+	// README §Subcommands shows this usage line for scan, and the help
+	// and the usage error both print it.
+	const want = "\n  sfdupes scan [--workers N] [-x] [--no-default-excludes] PATH...\n"
+
+	cases := map[string][]string{
+		"help":          {cmdScan, "-h"},
+		"missing paths": {cmdScan},
+	}
+
+	for name, args := range cases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			var stdout, stderr bytes.Buffer
+
+			run(args, &stdout, &stderr)
+
+			if !strings.Contains(stderr.String(), want) {
+				t.Errorf("run(%v) stderr = %q, want the usage line %q",
+					args, stderr.String(), want)
+			}
+		})
+	}
+}
+
 func TestRunVersion(t *testing.T) {
 	t.Parallel()
 

internal/sfdupes/progress.go

@@ -11,7 +11,6 @@ import (
 	"time"
 	"unicode/utf8"
 
-	"github.com/rivo/uniseg"
 	"github.com/schollz/progressbar/v3"
 	"golang.org/x/term"
 )
@@ -117,8 +116,7 @@ type drawnCount struct {
 // terminal's width. A phase with an exact total ends the line with its
 // percent and bar, at the terminal's right edge, when the terminal has
 // room for them. It is drawn again every redrawInterval, so its elapsed
-// time keeps moving while the phase waits for its next item. Each draw
+// time keeps moving while the phase waits for its next item. When
-// of the walk shows the path it reached last on the line below. When
 // stderr is not a TTY it emits no ANSI redraws: it prints line as the
 // phase starts, every plainInterval while it runs, and as it ends.
 //
@@ -143,7 +141,6 @@ type progress struct {
 	estimate   bool
 	waitingFor string
 	stalledOn  string
-	path       string // the path the walk reached last; "" for none
 	count      int64
 	start      time.Time // when the phase started, for the elapsed time
 	rateStart  time.Time // when the count started, for the time remaining
@@ -242,48 +239,6 @@ func (p *progress) draw() {
 	// less the terminal's last column, which spinnerMargin keeps clear. A
 	// bar's cells take one column each but more than one byte.
 	p.widest = max(p.widest, utf8.RuneCountInString(text)+spinnerMargin-1)
-
-	if p.path != "" {
-		// The library draws the path on the line below and returns to
-		// the phase's line. The path stays clear of the last column, so
-		// that no terminal wraps it.
-		_ = p.bar.AddDetail(cutToColumns(escapePath(p.path), width-1))
-	}
-}
-
-// cutToColumns returns s cut to at most columns terminal columns, at a
-// character boundary. A wide character, as in Chinese, takes two
-// columns.
-func cutToColumns(s string, columns int) string {
-	used, end, state := 0, 0, -1
-
-	for rest := s; rest != ""; {
-		char, next, width, nextState := uniseg.FirstGraphemeClusterInString(
-			rest, state)
-		if used+width > columns {
-			break
-		}
-
-		used += width
-		end += len(char)
-		rest, state = next, nextState
-	}
-
-	return s[:end]
-}
-
-// clear erases the display from the terminal: its line, and the path on
-// the line below when one is shown. p.mu must be held.
-func (p *progress) clear() {
-	if p.bar == nil {
-		return
-	}
-
-	if p.path != "" {
-		_ = p.bar.AddDetail("")
-	}
-
-	_ = p.bar.Clear()
 }
 
 // newBar has the library make what draw draws: its spinner, followed by
@@ -308,8 +263,6 @@ func (p *progress) newBar(width int) {
 		// The text carries the elapsed time and the time remaining.
 		progressbar.OptionSetElapsedTime(false),
 		progressbar.OptionSetPredictTime(false),
-		// The line below the phase's line, for the walk's path.
-		progressbar.OptionSetMaxDetailRow(1),
 	)
 	p.widest = 0
 }
@@ -361,19 +314,6 @@ func (p *progress) increment() {
 	p.lastItem = now
 }
 
-// setPath records the path the walk reached last, which a display on a
-// terminal shows at its next draw.
-func (p *progress) setPath(path string) {
-	if p == nil {
-		return
-	}
-
-	p.mu.Lock()
-	defer p.mu.Unlock()
-
-	p.path = path
-}
-
 // warnf prints a one-line warning to stderr without corrupting the
 // display. The whole message is escaped like a report's path columns,
 // so a path holding a newline cannot split the warning.
@@ -387,9 +327,11 @@ func (p *progress) warnf(format string, args ...any) {
 	p.mu.Lock()
 	defer p.mu.Unlock()
 
-	// The warning takes the display's line; the next draw shows the
+	if p.bar != nil {
-	// display again, on the line below.
+		// The warning takes the display's line; the next draw shows
-	p.clear()
+		// the display again, on the line below.
+		_ = p.bar.Clear()
+	}
 
 	fmt.Fprintln(os.Stderr, msg)
 }
@@ -450,7 +392,9 @@ func (w *progressWriter) Flush() error {
 		w.p.mu.Lock()
 		defer w.p.mu.Unlock()
 
-		w.p.clear()
+		if w.p.bar != nil {
+			_ = w.p.bar.Clear()
+		}
 	}
 
 	_, err := w.out.Write(w.buf)
@@ -470,13 +414,6 @@ func (p *progress) finish() {
 	close(p.stop)
 	<-p.done
 
-	// The walk's path is only for someone watching the walk. Its line is
-	// erased, and the next phase is drawn on it.
-	p.mu.Lock()
-	p.clear()
-	p.path = ""
-	p.mu.Unlock()
-
 	p.draw()
 
 	if p.width != nil {

internal/sfdupes/progress_test.go

@@ -6,7 +6,6 @@ import (
 	"math"
 	"os"
 	"path/filepath"
-	"regexp"
 	"slices"
 	"strings"
 	"sync"
@@ -1139,106 +1138,3 @@ func TestWarningAfterLastItemKeepsBar(t *testing.T) {
 		t.Errorf("terminal shows %q, want a count of 2 of 2", shown)
 	}
 }
-
-func TestCutToColumns(t *testing.T) {
-	t.Parallel()
-
-	cases := []struct {
-		s       string
-		columns int
-		want    string
-	}{
-		{"/srv/a", 10, "/srv/a"},
-		{"/srv/photos", 8, "/srv/pho"},
-		// Each of these two fullwidth letters takes two columns.
-		{"/ＡＢ/a", 4, "/Ａ"},
-		{"/ＡＢ/a", 5, "/ＡＢ"},
-		// An accent that combines with the letter before stays with it.
-		{"/café/a", 5, "/café"},
-		{"/srv", 0, ""},
-	}
-
-	for _, tc := range cases {
-		if got := cutToColumns(tc.s, tc.columns); got != tc.want {
-			t.Errorf("cutToColumns(%q, %d) = %q, want %q",
-				tc.s, tc.columns, got, tc.want)
-		}
-	}
-}
-
-// pathLines returns the text of each line the library wrote below a
-// display's line. It writes one as an erase to the end of the line, a
-// carriage return, the text and a newline.
-func pathLines(out string) []string {
-	matches := regexp.MustCompile("\x1b\\[K\r([^\n]*)\n").
-		FindAllStringSubmatch(out, -1)
-	lines := make([]string, 0, len(matches))
-
-	for _, m := range matches {
-		lines = append(lines, m[1])
-	}
-
-	return lines
-}
-
-// TestTerminalWalkShowsPathBelow checks that the walk's display on a
-// terminal 30 columns wide shows the path it reached last on the line
-// below, cut to 29 columns. That line is erased before a warning is
-// printed, and again when the walk ends, so the next phase is drawn on
-// an empty line.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestTerminalWalkShowsPathBelow(t *testing.T) {
-	stderr := captureStderr(t)
-	p := startProgress(progressParams{
-		label: scanPhase("walk"), unit: scanUnit, total: -1,
-	}, func() int { return 30 }, testRedraw, time.Now)
-
-	const shown = "/srv/photos/2026/holiday/beac"
-
-	p.setPath("/srv/photos/2026/holiday/beach.jpg")
-	p.increment()
-	awaitOutput(t, stderr, shown, 1)
-
-	p.warnf("warning")
-
-	before, _, _ := strings.Cut(stderr(), "warning")
-	if lines := pathLines(before); lines[len(lines)-1] != "" {
-		t.Errorf("line below shows %q as the warning is printed, want it "+
-			"empty", lines[len(lines)-1])
-	}
-
-	// Drawn again below the warning.
-	awaitOutput(t, stderr, shown, strings.Count(before, shown)+1)
-	p.finish()
-
-	lines := pathLines(stderr())
-	if !slices.Contains(lines, shown) {
-		t.Errorf("lines below the display = %q, want %q among them",
-			lines, shown)
-	}
-
-	if last := lines[len(lines)-1]; last != "" {
-		t.Errorf("line below the display shows %q after the walk, want it "+
-			"empty", last)
-	}
-}
-
-// TestPlainWalkShowsNoPath checks that the walk's display prints no path
-// when stderr is not a terminal.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestPlainWalkShowsNoPath(t *testing.T) {
-	stderr := captureStderr(t)
-	p := startProgress(progressParams{
-		label: scanPhase("walk"), unit: scanUnit, total: -1,
-	}, nil, testRedraw, time.Now)
-
-	p.setPath("/srv/a")
-	p.increment()
-	p.finish()
-
-	if strings.Contains(stderr(), "/srv/a") {
-		t.Errorf("stderr = %q, want no path", stderr())
-	}
-}

internal/sfdupes/report.go

@@ -195,10 +195,11 @@ func (w *reportWriter) add(r scanRec) error {
 }
 
 // endGroup ends the paths read with w.sig: two or more are a duplicate
-// group, held with its paths sorted until writeGroups writes it.
+// group, held with its paths sorted until writeGroups writes it. Empty
+// files form no group, since removing one frees nothing.
 func (w *reportWriter) endGroup() {
-	if len(w.paths) < minGroupSize {
+	if len(w.paths) < minGroupSize || w.sig.size == 0 {
-		// A path with no duplicate is dropped, and its slice reused.
+		// The paths are dropped, and their slice reused.
 		w.paths = w.paths[:0]
 
 		return

internal/sfdupes/report_test.go

@@ -434,6 +434,27 @@ func TestDupeGroups(t *testing.T) {
 	}
 }
 
+// TestDupeGroupsLeavesOutEmptyFiles checks that empty files form no
+// duplicate group, while 1-byte files still do.
+func TestDupeGroupsLeavesOutEmptyFiles(t *testing.T) {
+	t.Parallel()
+
+	e, x := sha256.Sum256(nil), testHash("x")
+	recs := []scanRec{
+		{size: 0, head: e, tail: e, content: e, path: "/a/.gitkeep"},
+		{size: 0, head: e, tail: e, content: e, path: "/b/.gitkeep"},
+		{size: 0, head: e, tail: e, content: e, path: "/c/__init__.py"},
+		{size: 1, head: x, tail: x, content: x, path: "/tiny1"},
+		{size: 1, head: x, tail: x, content: x, path: "/tiny2"},
+	}
+
+	groups := dupeGroupsOf(t, recs)
+	if len(groups) != 1 || groups[0].size != 1 ||
+		!slices.Equal(groups[0].paths, []string{"/tiny1", "/tiny2"}) {
+		t.Fatalf("groups = %+v, want only /tiny1 /tiny2 of size 1", groups)
+	}
+}
+
 func TestDupeGroupsContentSeparates(t *testing.T) {
 	t.Parallel()
 

internal/sfdupes/scan.go

@@ -542,7 +542,6 @@ func (s *scanState) walkPhase(events <-chan walkEvent, roots []string) {
 
 		s.st.walked++
 
-		prog.setPath(ev.rec.path)
 		prog.increment()
 
 		old, ok := s.existing[ev.rec.path]

internal/sfdupes/scan_test.go

@@ -1185,11 +1185,12 @@ func assertSmokeDupeGroups(t *testing.T, dir string, db *sql.DB) {
 	t.Helper()
 
 	groups := dupeGroups(t, db)
-	if len(groups) != 5 {
+	if len(groups) != 4 {
-		t.Fatalf("len(groups) = %d, want 5", len(groups))
+		t.Fatalf("len(groups) = %d, want 4", len(groups))
 	}
 
-	wantSizes := []int64{3000, 2000, 100, 1, 0}
+	// The empty files empty1 and empty2 form no group.
+	wantSizes := []int64{3000, 2000, 100, 1}
 	for i, g := range groups {
 		if g.size != wantSizes[i] {
 			t.Errorf("groups[%d].size = %d, want %d",
@@ -2367,8 +2368,8 @@ func TestRunScanPassesOverDatabase(t *testing.T) {
 			report := runStdout(t, cmdReport)
 			if strings.Contains(report, "db.sqlite") ||
 				strings.Contains(report, hardLink) ||
-				!strings.Contains(report, filepath.Join(tree, "empty2")) {
+				!strings.Contains(report, filepath.Join(tree, "b")) {
-				t.Errorf("report = %q, want the empty files and none of "+
+				t.Errorf("report = %q, want a and b and none of "+
 					"the database's files", report)
 			}
 		})

internal/sfdupes/trees.go

@@ -301,7 +301,9 @@ func fileEntry(name string, r scanRec) string {
 // collectTreeGroups groups directories by digest, counting each one on
 // prog as it is grouped, and returns every maximal group with two or
 // more members, each group's members sorted by path, groups ordered by
-// tree size descending then by first path ascending.
+// tree size descending then by first path ascending. A group whose
+// trees hold 0 bytes is left out, since removing one frees nothing. The
+// groups it implies hold 0 bytes too, so leaving it out hides nothing.
 func collectTreeGroups(allDirs []*treeNode, super *treeNode,
 	prog *progress,
 ) [][]*treeNode {
@@ -315,7 +317,9 @@ func collectTreeGroups(allDirs []*treeNode, super *treeNode,
 	var dupes [][]*treeNode
 
 	for _, g := range groups {
-		if len(g) < minGroupSize || suppressed(g, super) {
+		// The members share a digest, so they share a total size.
+		if len(g) < minGroupSize || g[0].totalSize == 0 ||
+			suppressed(g, super) {
 			continue
 		}
 

internal/sfdupes/trees_test.go

@@ -2,6 +2,7 @@ package sfdupes //nolint:testpackage // checks the unexported treeNode results
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"database/sql"
 	"os"
 	"slices"
@@ -435,6 +436,35 @@ func TestCollectTreeGroupsSiblings(t *testing.T) {
 	}
 }
 
+// TestCollectTreeGroupsLeavesOutEmptyTrees checks that directories
+// holding only empty files form no group, and that an empty file still
+// counts toward the digest of a tree that holds other files.
+func TestCollectTreeGroupsLeavesOutEmptyTrees(t *testing.T) {
+	t.Parallel()
+
+	h, tl, c, e := testHash("h"), testHash("t"), testHash("c"),
+		sha256.Sum256(nil)
+	recs := []scanRec{
+		{size: 0, head: e, tail: e, content: e, path: "/e/a/.gitkeep"},
+		{size: 0, head: e, tail: e, content: e, path: "/e/b/.gitkeep"},
+		{size: 10, head: h, tail: tl, content: c, path: "/p/x1/f"},
+		{size: 0, head: e, tail: e, content: e, path: "/p/x1/.gitkeep"},
+		{size: 10, head: h, tail: tl, content: c, path: "/p/x2/f"},
+		{size: 0, head: e, tail: e, content: e, path: "/p/x2/.gitkeep"},
+		// Without the empty file, /p/x3 is no copy of /p/x1.
+		{size: 10, head: h, tail: tl, content: c, path: "/p/x3/f"},
+	}
+
+	super, dirs := treeOf(t, recs)
+
+	got := groupPaths(collectTreeGroups(dirs, super, nil))
+
+	want := [][]string{{"/p/x1", "/p/x2"}}
+	if !slices.EqualFunc(got, want, slices.Equal) {
+		t.Fatalf("groups = %v, want %v", got, want)
+	}
+}
+
 func TestCollectTreeGroupsDifferingParents(t *testing.T) {
 	t.Parallel()