TODO.md: keep only open work (closes #167)

Remove the Completed Steps section and the Status sentence saying the
file records history. Git keeps the history. The Workflow step that
recorded finished work in Completed Steps now deletes Next Step instead.

Model: opus-5-5

README.md

@@ -128,8 +128,8 @@ walk"). As the file `/etc/cron.d/sfdupes`:
     - one line naming the database;
     - progress lines, as described under "Progress";
     - a warning for each path it skips;
-    - a line for each system, temporary or cache directory the walk leaves out
+    - a line for each system or temporary directory the walk leaves out (see
-      (see "Rules for the walk");
+      "Rules for the walk");
     - a line for each path left out because its filesystem is one the kernel,
       the core of the operating system, makes up or keeps in memory, such as
       `tmpfs`;
@@ -300,9 +300,8 @@ The reference below is also the program's specification.
   of directories on other filesystems, as the same flag does for `du` and
   `rsync`. By default the walk also enters directories on other filesystems.
 - `--no-default-excludes` (`scan`, `dwim`) lets the walk enter the default
-  excludes. Those are the system, temporary and cache directories the walk
+  excludes. Those are the system and temporary directories the walk otherwise
-  otherwise leaves out, such as `/var/tmp` and `/var/cache` on Linux (see "Rules
+  leaves out, such as `/var/tmp` on Linux (see "Rules for the walk").
-  for the walk").
 - `--exclude PATH` (`scan`, `dwim`) keeps the walk out of `PATH` and everything
   below it. `PATH` may be a directory or a file. The flag may be given more than
   once. The walk knows `PATH` by its device ID and inode number, as it knows the
@@ -572,17 +571,12 @@ walk practical on large or busy storage pools.
     `--no-default-excludes` does not change this rule.
 
 - Below an operand, the walk does not enter a default exclude. On Linux, the
-  default excludes hold the kernel's view of the running system, temporary
+  default excludes hold temporary files and the kernel's view of the running
-  files, and caches. A cache here is data that programs and package managers
+  system. They depend on the system, and `sfdupes scan --help` lists those of
-  download or build again on their own. The default excludes depend on the
+  the system it runs on. On Linux they are:
-  system, and `sfdupes scan --help` lists those of the system it runs on. In the
-  lists, `*` stands for any one directory name, so `/home/*/.cache` matches
-  `/home/alice/.cache`. On Linux they are:
 
     ```
-    /proc, /sys, /dev, /run, /tmp, /var/tmp, /var/cache
+    /proc, /sys, /dev, /run, /tmp, /var/tmp
-    /root/.cache, /root/.npm, /root/.cargo/registry, /root/go/pkg/mod
-    /home/*/.cache, /home/*/.npm, /home/*/.cargo/registry, /home/*/go/pkg/mod
     ```
 
     On macOS they are:
@@ -590,21 +584,13 @@ walk practical on large or busy storage pools.
     ```
     /dev, /private/tmp, /private/var/tmp, /private/var/vm
     /System/Volumes/VM, /System/Volumes/Data
-    /private/var/folders, /Library/Caches
-    /private/var/root/Library/Caches, /private/var/root/.cache
-    /private/var/root/.npm, /private/var/root/.cargo/registry
-    /private/var/root/go/pkg/mod
-    /Users/*/Library/Caches, /Users/*/.cache, /Users/*/.npm
-    /Users/*/.cargo/registry, /Users/*/go/pkg/mod
     ```
 
-    `/private/var/folders` holds each user's temporary files and caches on
+    A walk of `/` on macOS reaches everything in `/System/Volumes/Data` already,
-    macOS. Root's home on macOS is `/var/root`, which the walk reaches as
+    through firmlinks. Firmlinks are the links macOS uses to show the data
-    `/private/var/root`. A walk of `/` on macOS reaches everything in
+    volume inside the system volume. Walking `/System/Volumes/Data` as well
-    `/System/Volumes/Data` already, through firmlinks. Firmlinks are the links
+    would record each of those files twice. Any other system has no default
-    macOS uses to show the data volume inside the system volume. Walking
+    excludes.
-    `/System/Volumes/Data` as well would record each of those files twice. Any
-    other system has no default excludes.
 
     An operand at or inside a default exclude is walked, so
     `sfdupes scan /tmp/x` works when `/tmp/x` is on a persistent filesystem.

internal/sfdupes/exclude.go

@@ -72,31 +72,14 @@ type walkRules struct {
 func defaultExcludes(goos string) []string {
 	switch goos {
 	case goosLinux:
-		// The kernel's view of the running system, temporary files, and
+		return []string{"/proc", "/sys", "/dev", "/run", "/tmp", "/var/tmp"}
-		// caches that programs and package managers fill again on their
-		// own: the system's, root's and those in each home in /home.
-		return []string{
-			"/proc", "/sys", "/dev", "/run", "/tmp", "/var/tmp", "/var/cache",
-			"/root/.cache", "/root/.npm", "/root/.cargo/registry",
-			"/root/go/pkg/mod",
-			"/home/*/.cache", "/home/*/.npm", "/home/*/.cargo/registry",
-			"/home/*/go/pkg/mod",
-		}
 	case goosDarwin:
 		// A walk of / reaches everything in /System/Volumes/Data through
 		// the firmlinks, so walking it as well would record each of
-		// those files twice. /private/var/folders holds each user's
+		// those files twice.
-		// temporary files and caches. The walk reaches root's home,
-		// /var/root, as /private/var/root.
 		return []string{
 			"/dev", "/private/tmp", "/private/var/tmp", "/private/var/vm",
 			"/System/Volumes/VM", "/System/Volumes/Data",
-			"/private/var/folders", "/Library/Caches",
-			"/private/var/root/Library/Caches", "/private/var/root/.cache",
-			"/private/var/root/.npm", "/private/var/root/.cargo/registry",
-			"/private/var/root/go/pkg/mod",
-			"/Users/*/Library/Caches", "/Users/*/.cache", "/Users/*/.npm",
-			"/Users/*/.cargo/registry", "/Users/*/go/pkg/mod",
 		}
 	case goosWindows:
 		// Relative to the root of the drive an operand lies on. The

internal/sfdupes/exclude_test.go

@@ -24,22 +24,10 @@ func TestDefaultExcludes(t *testing.T) {
 	// 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: {
+		goosLinux: {"/proc", "/sys", "/dev", "/run", "/tmp", "/var/tmp"},
-			"/proc", "/sys", "/dev", "/run", "/tmp", "/var/tmp", "/var/cache",
-			"/root/.cache", "/root/.npm", "/root/.cargo/registry",
-			"/root/go/pkg/mod",
-			"/home/*/.cache", "/home/*/.npm", "/home/*/.cargo/registry",
-			"/home/*/go/pkg/mod",
-		},
 		goosDarwin: {
 			"/dev", "/private/tmp", "/private/var/tmp", "/private/var/vm",
 			"/System/Volumes/VM", "/System/Volumes/Data",
-			"/private/var/folders", "/Library/Caches",
-			"/private/var/root/Library/Caches", "/private/var/root/.cache",
-			"/private/var/root/.npm", "/private/var/root/.cargo/registry",
-			"/private/var/root/go/pkg/mod",
-			"/Users/*/Library/Caches", "/Users/*/.cache", "/Users/*/.npm",
-			"/Users/*/.cargo/registry", "/Users/*/go/pkg/mod",
 		},
 		goosWindows: {
 			"pagefile.sys", "swapfile.sys", "hiberfil.sys",
@@ -75,29 +63,6 @@ func TestIsDefaultExclude(t *testing.T) {
 			t.Errorf("isDefaultExclude(%q) = %v, want %v", path, got, want)
 		}
 	}
-
-	// The Linux list matches the cache directories in /root and in each
-	// home in /home, but nothing below them and no .cache directory
-	// elsewhere.
-	linux := map[string]bool{
-		"/home/u/.cache":           true,
-		"/home/u/go/pkg/mod":       true,
-		"/root/.cache":             true,
-		"/var/cache":               true,
-		"/home/u/.cache/pip":       false,
-		"/home/u/src/.cache":       false,
-		"/srv/home/u/.cache":       false,
-		"/home/u/.cargo/bin":       false,
-		"/home/u/go/pkg/mod/cache": false,
-	}
-
-	for path, want := range linux {
-		got := isDefaultExclude(path, defaultExcludes(goosLinux))
-		if got != want {
-			t.Errorf("isDefaultExclude(%q, Linux list) = %v, want %v", path,
-				got, want)
-		}
-	}
 }
 
 func TestReadMountInfo(t *testing.T) {
@@ -325,7 +290,7 @@ func TestRunScanTempDirOperand(t *testing.T) {
 	t.Setenv(databaseEnv, path)
 
 	dir := realTempDir(t)
-	if !insideDefaultExclude(dir, defaultExcludes(runtime.GOOS)) {
+	if !underAnyRoot(dir, defaultExcludes(runtime.GOOS)) {
 		t.Skip(dir + " is not inside a default exclude")
 	}
 
@@ -746,20 +711,6 @@ func shmTempDir(t *testing.T) (string, string, walkRules) {
 	return dir, fsType, walkRules{nonPersistent: nonPersistent}
 }
 
-// insideDefaultExclude reports whether path, which is absolute and
-// clean, or a directory above it is one of excludes.
-func insideDefaultExclude(path string, excludes []string) bool {
-	for dir := path; ; dir = filepath.Dir(dir) {
-		if isDefaultExclude(dir, excludes) {
-			return true
-		}
-
-		if dir == "/" {
-			return false
-		}
-	}
-}
-
 // assertRecorded checks that the database at dbPath holds a record for
 // path when want is set, and none when it is not.
 func assertRecorded(t *testing.T, dbPath, path string, want bool) {