takt: reviewコマンドにて、差分を確認するメニューを用意してほしい。その場でgitdiffをするような形かな。

src/__tests__/reviewTasks.test.ts

@@ -2,14 +2,14 @@
  * Tests for review-tasks command
  */
 
-import { describe, it, expect } from 'vitest';
+import { describe, it, expect, vi } from 'vitest';
 import {
   parseTaktWorktrees,
   extractTaskSlug,
   buildReviewItems,
   type WorktreeInfo,
 } from '../task/worktree.js';
-import { isBranchMerged, type ReviewAction } from '../commands/reviewTasks.js';
+import { isBranchMerged, showFullDiff, type ReviewAction } from '../commands/reviewTasks.js';
 
 describe('parseTaktWorktrees', () => {
   it('should parse takt/ branches from porcelain output', () => {
@@ -170,14 +170,35 @@ describe('buildReviewItems', () => {
 });
 
 describe('ReviewAction type', () => {
-  it('should include try, merge, delete (no skip)', () => {
-    const actions: ReviewAction[] = ['try', 'merge', 'delete'];
-    expect(actions).toHaveLength(3);
+  it('should include diff, try, merge, delete', () => {
+    const actions: ReviewAction[] = ['diff', 'try', 'merge', 'delete'];
+    expect(actions).toHaveLength(4);
+    expect(actions).toContain('diff');
     expect(actions).toContain('try');
+    expect(actions).toContain('merge');
+    expect(actions).toContain('delete');
     expect(actions).not.toContain('skip');
   });
 });
 
+describe('showFullDiff', () => {
+  it('should not throw for non-existent project dir', () => {
+    // spawnSync will fail gracefully; showFullDiff catches errors
+    expect(() => showFullDiff('/non-existent-dir', 'main', 'some-branch')).not.toThrow();
+  });
+
+  it('should not throw for non-existent branch', () => {
+    expect(() => showFullDiff('/tmp', 'main', 'non-existent-branch-xyz')).not.toThrow();
+  });
+
+  it('should warn when diff fails', () => {
+    const warnSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    showFullDiff('/non-existent-dir', 'main', 'some-branch');
+    warnSpy.mockRestore();
+    // No assertion needed — the test verifies it doesn't throw
+  });
+});
+
 describe('isBranchMerged', () => {
   it('should return false for non-existent project dir', () => {
     // git merge-base will fail on non-existent dir

src/commands/reviewTasks.ts

@@ -5,7 +5,7 @@
  * try merge, merge & cleanup, or delete actions.
  */
 
-import { execFileSync } from 'node:child_process';
+import { execFileSync, spawnSync } from 'node:child_process';
 import chalk from 'chalk';
 import {
   removeWorktree,
@@ -21,7 +21,7 @@ import { createLogger } from '../utils/debug.js';
 const log = createLogger('review-tasks');
 
 /** Actions available for a reviewed worktree */
-export type ReviewAction = 'try' | 'merge' | 'delete';
+export type ReviewAction = 'diff' | 'try' | 'merge' | 'delete';
 
 /**
  * Check if a branch has already been merged into HEAD.
@@ -39,6 +39,28 @@ export function isBranchMerged(projectDir: string, branch: string): boolean {
   }
 }
 
+/**
+ * Show full diff in an interactive pager (less).
+ * Falls back to direct output if pager is unavailable.
+ */
+export function showFullDiff(
+  cwd: string,
+  defaultBranch: string,
+  branch: string,
+): void {
+  try {
+    const result = spawnSync(
+      'git', ['diff', '--color=always', `${defaultBranch}...${branch}`],
+      { cwd, stdio: ['inherit', 'inherit', 'inherit'], env: { ...process.env, GIT_PAGER: 'less -R' } },
+    );
+    if (result.status !== 0) {
+      warn('Could not display diff');
+    }
+  } catch {
+    warn('Could not display diff');
+  }
+}
+
 /**
  * Show diff stat for a branch and prompt for an action.
  */
@@ -66,6 +88,7 @@ async function showDiffAndPromptAction(
   const action = await selectOption<ReviewAction>(
     `Action for ${item.info.branch}:`,
     [
+      { label: 'View diff', value: 'diff', description: 'Show full diff in pager' },
       { label: 'Try merge', value: 'try', description: 'Merge without cleanup (keep worktree & branch)' },
       { label: 'Merge & cleanup', value: 'merge', description: 'Merge (if needed) and remove worktree & branch' },
       { label: 'Delete', value: 'delete', description: 'Discard changes, remove worktree and branch' },
@@ -214,7 +237,15 @@ export async function reviewTasks(cwd: string): Promise<void> {
     const item = items[selectedIdx];
     if (!item) continue;
 
-    const action = await showDiffAndPromptAction(cwd, defaultBranch, item);
+    // Action loop: re-show menu after viewing diff
+    let action: ReviewAction | null;
+    do {
+      action = await showDiffAndPromptAction(cwd, defaultBranch, item);
+
+      if (action === 'diff') {
+        showFullDiff(cwd, defaultBranch, item.info.branch);
+      }
+    } while (action === 'diff');
 
     if (action === null) continue;