Step 7: Remaining commands — remove, verify, list, diff.

Remove: untrack files, remove manifest entries, save. 2 tests.
Verify: check blobs against manifest hashes, report ok/mismatch/missing. 3 tests.
List: return all tracked entries, CLI formats by type. 2 tests.
Diff: compare stored blob vs current file, simple line diff. 3 tests.

Each command in its own file (garden/<cmd>.go) for parallel development.
Remove, verify, list implemented by parallel worktree agents; diff manual.

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

garden/diff_test.go

@@ -0,0 +1,94 @@
+package garden
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestDiffUnchangedFile(t *testing.T) {
+	root := t.TempDir()
+	repoDir := filepath.Join(root, "repo")
+
+	g, err := Init(repoDir)
+	if err != nil {
+		t.Fatalf("Init: %v", err)
+	}
+
+	testFile := filepath.Join(root, "testfile")
+	if err := os.WriteFile(testFile, []byte("hello world\n"), 0o644); err != nil {
+		t.Fatalf("writing test file: %v", err)
+	}
+
+	if err := g.Add([]string{testFile}); err != nil {
+		t.Fatalf("Add: %v", err)
+	}
+
+	d, err := g.Diff(testFile)
+	if err != nil {
+		t.Fatalf("Diff: %v", err)
+	}
+
+	if d != "" {
+		t.Errorf("expected empty diff for unchanged file, got:\n%s", d)
+	}
+}
+
+func TestDiffModifiedFile(t *testing.T) {
+	root := t.TempDir()
+	repoDir := filepath.Join(root, "repo")
+
+	g, err := Init(repoDir)
+	if err != nil {
+		t.Fatalf("Init: %v", err)
+	}
+
+	testFile := filepath.Join(root, "testfile")
+	if err := os.WriteFile(testFile, []byte("original\n"), 0o644); err != nil {
+		t.Fatalf("writing test file: %v", err)
+	}
+
+	if err := g.Add([]string{testFile}); err != nil {
+		t.Fatalf("Add: %v", err)
+	}
+
+	// Modify the file on disk.
+	if err := os.WriteFile(testFile, []byte("modified\n"), 0o644); err != nil {
+		t.Fatalf("modifying test file: %v", err)
+	}
+
+	d, err := g.Diff(testFile)
+	if err != nil {
+		t.Fatalf("Diff: %v", err)
+	}
+
+	if d == "" {
+		t.Fatal("expected non-empty diff for modified file")
+	}
+
+	if !strings.Contains(d, "original") {
+		t.Errorf("diff should contain old content 'original', got:\n%s", d)
+	}
+	if !strings.Contains(d, "modified") {
+		t.Errorf("diff should contain new content 'modified', got:\n%s", d)
+	}
+	if !strings.Contains(d, "---") || !strings.Contains(d, "+++") {
+		t.Errorf("diff should contain --- and +++ headers, got:\n%s", d)
+	}
+}
+
+func TestDiffUntrackedPath(t *testing.T) {
+	root := t.TempDir()
+	repoDir := filepath.Join(root, "repo")
+
+	g, err := Init(repoDir)
+	if err != nil {
+		t.Fatalf("Init: %v", err)
+	}
+
+	_, err = g.Diff(filepath.Join(root, "nonexistent"))
+	if err == nil {
+		t.Fatal("expected error for untracked path")
+	}
+}