Add directory recursion for Add and mirror up/down commands.

Add now recursively walks directories instead of creating a single
"directory" type entry. Extract addEntry helper for reuse. Implement
MirrorUp (sync filesystem state into manifest) and MirrorDown (sync
manifest state to filesystem with untracked file cleanup). Add CLI
mirror command with up/down subcommands.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

garden/garden.go

@@ -98,9 +98,55 @@ func (g *Garden) SetClock(c clockwork.Clock) {
 	g.clock = c
 }
 
+// addEntry adds a single file or symlink to the manifest. The abs path must
+// already be resolved and info must come from os.Lstat. If skipDup is true,
+// already-tracked paths are silently skipped instead of returning an error.
+func (g *Garden) addEntry(abs string, info os.FileInfo, now time.Time, skipDup bool) error {
+	tilded := toTildePath(abs)
+
+	if g.findEntry(tilded) != nil {
+		if skipDup {
+			return nil
+		}
+		return fmt.Errorf("already tracking %s", tilded)
+	}
+
+	entry := manifest.Entry{
+		Path:    tilded,
+		Mode:    fmt.Sprintf("%04o", info.Mode().Perm()),
+		Updated: now,
+	}
+
+	switch {
+	case info.Mode()&os.ModeSymlink != 0:
+		target, err := os.Readlink(abs)
+		if err != nil {
+			return fmt.Errorf("reading symlink %s: %w", abs, err)
+		}
+		entry.Type = "link"
+		entry.Target = target
+
+	default:
+		data, err := os.ReadFile(abs)
+		if err != nil {
+			return fmt.Errorf("reading file %s: %w", abs, err)
+		}
+		hash, err := g.store.Write(data)
+		if err != nil {
+			return fmt.Errorf("storing blob for %s: %w", abs, err)
+		}
+		entry.Type = "file"
+		entry.Hash = hash
+	}
+
+	g.manifest.Files = append(g.manifest.Files, entry)
+	return nil
+}
+
 // Add tracks new files, directories, or symlinks. Each path is resolved
 // to an absolute path, inspected for its type, and added to the manifest.
-// Regular files are hashed and stored in the blob store.
+// Regular files are hashed and stored in the blob store. Directories are
+// recursively walked and all leaf files and symlinks are added individually.
 func (g *Garden) Add(paths []string) error {
 	now := g.clock.Now().UTC()
 
@@ -115,45 +161,29 @@ func (g *Garden) Add(paths []string) error {
 			return fmt.Errorf("stat %s: %w", abs, err)
 		}
 
-		tilded := toTildePath(abs)
-
-		// Check if already tracked.
-		if g.findEntry(tilded) != nil {
-			return fmt.Errorf("already tracking %s", tilded)
-		}
-
-		entry := manifest.Entry{
-			Path:    tilded,
-			Mode:    fmt.Sprintf("%04o", info.Mode().Perm()),
-			Updated: now,
-		}
-
-		switch {
-		case info.Mode()&os.ModeSymlink != 0:
-			target, err := os.Readlink(abs)
+		if info.IsDir() {
+			// Recursively walk the directory, adding all files and symlinks.
+			err := filepath.WalkDir(abs, func(path string, d os.DirEntry, err error) error {
+				if err != nil {
+					return err
+				}
+				if d.IsDir() {
+					return nil // skip directory entries themselves
+				}
+				fi, err := os.Lstat(path)
+				if err != nil {
+					return fmt.Errorf("stat %s: %w", path, err)
+				}
+				return g.addEntry(path, fi, now, true)
+			})
 			if err != nil {
-				return fmt.Errorf("reading symlink %s: %w", abs, err)
+				return fmt.Errorf("walking directory %s: %w", abs, err)
 			}
-			entry.Type = "link"
-			entry.Target = target
-
-		case info.IsDir():
-			entry.Type = "directory"
-
-		default:
-			data, err := os.ReadFile(abs)
-			if err != nil {
-				return fmt.Errorf("reading file %s: %w", abs, err)
+		} else {
+			if err := g.addEntry(abs, info, now, false); err != nil {
+				return err
 			}
-			hash, err := g.store.Write(data)
-			if err != nil {
-				return fmt.Errorf("storing blob for %s: %w", abs, err)
-			}
-			entry.Type = "file"
-			entry.Hash = hash
 		}
-
-		g.manifest.Files = append(g.manifest.Files, entry)
 	}
 
 	g.manifest.Updated = now