feat: phase 3 for git integration

tests/engine/GitEngine.test.ts

@@ -4,6 +4,7 @@ const mockVersion = vi.fn();
 const mockCheckIsRepo = vi.fn();
 const mockRevparse = vi.fn();
 const mockStatus = vi.fn();
+const mockDiff = vi.fn();
 const mockInit = vi.fn();
 const mockRaw = vi.fn();
 const mockAdd = vi.fn();
@@ -30,6 +31,7 @@ vi.mock('simple-git', () => ({
     checkIsRepo: mockCheckIsRepo,
     revparse: mockRevparse,
     status: mockStatus,
+    diff: mockDiff,
     init: mockInit,
     raw: mockRaw,
     add: mockAdd,
@@ -139,6 +141,20 @@ describe('GitEngine', () => {
     });
   });
 
+  describe('getDiff', () => {
+    it('should return patch output for a repository file', async () => {
+      mockDiff.mockResolvedValue('diff --git a/posts/first.md b/posts/first.md\n+hello');
+
+      const result = await gitEngine.getDiff('/tmp/project', 'posts/first.md');
+
+      expect(mockDiff).toHaveBeenCalledWith(['--', 'posts/first.md']);
+      expect(result).toEqual({
+        filePath: 'posts/first.md',
+        patch: 'diff --git a/posts/first.md b/posts/first.md\n+hello',
+      });
+    });
+  });
+
   describe('ensureGitignore', () => {
     it('should create .gitignore with default system metadata entries when missing', async () => {
       mockReadFile.mockRejectedValue(new Error('ENOENT'));

tests/ipc/handlers.test.ts

@@ -144,6 +144,7 @@ const mockGitEngine = {
   checkAvailability: vi.fn(),
   getRepoState: vi.fn(),
   getStatus: vi.fn(),
+  getDiff: vi.fn(),
   initializeRepo: vi.fn(),
   ensureGitignore: vi.fn(),
   pruneLfsCache: vi.fn(),
@@ -318,6 +319,23 @@ describe('IPC Handlers', () => {
       });
     });
 
+    describe('git:diff', () => {
+      it('should pass project path and file path to GitEngine.getDiff', async () => {
+        mockGitEngine.getDiff.mockResolvedValue({
+          filePath: 'posts/first.md',
+          patch: 'diff --git a/posts/first.md b/posts/first.md',
+        });
+
+        const result = await invokeHandler('git:diff', '/repo', 'posts/first.md');
+
+        expect(mockGitEngine.getDiff).toHaveBeenCalledWith('/repo', 'posts/first.md');
+        expect(result).toEqual({
+          filePath: 'posts/first.md',
+          patch: 'diff --git a/posts/first.md b/posts/first.md',
+        });
+      });
+    });
+
     describe('git:init', () => {
       it('should pass project path to GitEngine.initializeRepo', async () => {
         mockGitEngine.initializeRepo.mockResolvedValue({ success: true });

tests/renderer/components/GitDiffView.test.tsx

@@ -0,0 +1,45 @@
+import React from 'react';
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { GitDiffView } from '../../../src/renderer/components/GitDiffView/GitDiffView';
+import { useAppStore } from '../../../src/renderer/store';
+
+describe('GitDiffView', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+
+    useAppStore.setState({
+      activeProject: {
+        id: 'project-1',
+        name: 'Test Project',
+        slug: 'test-project',
+        isActive: true,
+        dataPath: '/repo/path',
+        createdAt: new Date().toISOString(),
+        updatedAt: new Date().toISOString(),
+      },
+    });
+
+    (window as any).electronAPI = {
+      ...(window as any).electronAPI,
+      git: {
+        ...(window as any).electronAPI?.git,
+        getDiff: vi.fn().mockResolvedValue({
+          filePath: 'posts/first.md',
+          patch: 'diff --git a/posts/first.md b/posts/first.md\n+hello',
+        }),
+      },
+      app: {
+        ...(window as any).electronAPI?.app,
+        getDefaultProjectPath: vi.fn().mockResolvedValue('/repo/path'),
+      },
+    };
+  });
+
+  it('loads and renders the git diff patch for the selected file', async () => {
+    render(<GitDiffView filePath="posts/first.md" />);
+
+    expect(await screen.findByText(/diff --git a\/posts\/first\.md b\/posts\/first\.md/i)).toBeInTheDocument();
+    expect((window as any).electronAPI.git.getDiff).toHaveBeenCalledWith('/repo/path', 'posts/first.md');
+  });
+});

tests/renderer/components/GitSidebar.test.tsx

@@ -4,6 +4,8 @@ import { render, screen, fireEvent, act } from '@testing-library/react';
 import { GitSidebar } from '../../../src/renderer/components/GitSidebar/GitSidebar';
 import { useAppStore } from '../../../src/renderer/store';
 
+const getStore = () => useAppStore.getState();
+
 describe('GitSidebar', () => {
   beforeEach(() => {
     vi.clearAllMocks();
@@ -17,6 +19,8 @@ describe('GitSidebar', () => {
         createdAt: new Date().toISOString(),
         updatedAt: new Date().toISOString(),
       },
+      tabs: [],
+      activeTabId: null,
     });
 
     (window as any).electronAPI = {
@@ -28,6 +32,8 @@ describe('GitSidebar', () => {
       git: {
         checkAvailability: vi.fn().mockResolvedValue({ gitFound: true, version: '2.49.0' }),
         getRepoState: vi.fn().mockResolvedValue({ isRepo: false, hasRemote: false }),
+        getStatus: vi.fn().mockResolvedValue({ files: [], counts: { untracked: 0, modified: 0, deleted: 0, renamed: 0, staged: 0, total: 0 } }),
+        getDiff: vi.fn().mockResolvedValue({ filePath: 'posts/a.md', patch: 'diff --git a/posts/a.md b/posts/a.md' }),
         init: vi.fn().mockResolvedValue({ success: true }),
         ensureGitignore: vi.fn().mockResolvedValue({ updated: false, created: false, addedEntries: [] }),
         onInitProgress: vi.fn().mockImplementation(() => () => {}),
@@ -49,6 +55,88 @@ describe('GitSidebar', () => {
     expect(await screen.findByRole('button', { name: /initialize git/i })).toBeInTheDocument();
   });
 
+  it('renders open changes list when repository exists', async () => {
+    (window as any).electronAPI.git.getRepoState = vi.fn().mockResolvedValue({
+      isRepo: true,
+      rootPath: '/repo/path',
+      currentBranch: 'main',
+      hasRemote: true,
+    });
+    (window as any).electronAPI.git.getStatus = vi.fn().mockResolvedValue({
+      files: [
+        { path: 'posts/first.md', status: 'modified' },
+        { path: 'posts/second.md', status: 'untracked' },
+      ],
+      counts: { untracked: 1, modified: 1, deleted: 0, renamed: 0, staged: 0, total: 2 },
+    });
+
+    render(<GitSidebar />);
+
+    expect(await screen.findByText(/open changes/i)).toBeInTheDocument();
+    expect(screen.getByText('posts/first.md')).toBeInTheDocument();
+    expect(screen.getByText('posts/second.md')).toBeInTheDocument();
+    expect(screen.getByText(/version history/i)).toBeInTheDocument();
+  });
+
+  it('single click opens and reuses a transient git-diff tab', async () => {
+    (window as any).electronAPI.git.getRepoState = vi.fn().mockResolvedValue({
+      isRepo: true,
+      rootPath: '/repo/path',
+      currentBranch: 'main',
+      hasRemote: true,
+    });
+    (window as any).electronAPI.git.getStatus = vi.fn().mockResolvedValue({
+      files: [
+        { path: 'posts/first.md', status: 'modified' },
+        { path: 'posts/second.md', status: 'untracked' },
+      ],
+      counts: { untracked: 1, modified: 1, deleted: 0, renamed: 0, staged: 0, total: 2 },
+    });
+
+    render(<GitSidebar />);
+
+    const first = await screen.findByRole('button', { name: /posts\/first\.md/i });
+    const second = screen.getByRole('button', { name: /posts\/second\.md/i });
+
+    await act(async () => {
+      fireEvent.click(first);
+    });
+
+    expect(getStore().tabs).toHaveLength(1);
+    expect(getStore().tabs[0]).toMatchObject({ type: 'git-diff', id: 'git-diff:posts/first.md', isTransient: true });
+
+    await act(async () => {
+      fireEvent.click(second);
+    });
+
+    expect(getStore().tabs).toHaveLength(1);
+    expect(getStore().tabs[0]).toMatchObject({ type: 'git-diff', id: 'git-diff:posts/second.md', isTransient: true });
+  });
+
+  it('double click opens a persistent git-diff tab', async () => {
+    (window as any).electronAPI.git.getRepoState = vi.fn().mockResolvedValue({
+      isRepo: true,
+      rootPath: '/repo/path',
+      currentBranch: 'main',
+      hasRemote: true,
+    });
+    (window as any).electronAPI.git.getStatus = vi.fn().mockResolvedValue({
+      files: [{ path: 'posts/first.md', status: 'modified' }],
+      counts: { untracked: 0, modified: 1, deleted: 0, renamed: 0, staged: 0, total: 1 },
+    });
+
+    render(<GitSidebar />);
+
+    const first = await screen.findByRole('button', { name: /posts\/first\.md/i });
+
+    await act(async () => {
+      fireEvent.doubleClick(first);
+    });
+
+    expect(getStore().tabs).toHaveLength(1);
+    expect(getStore().tabs[0]).toMatchObject({ type: 'git-diff', id: 'git-diff:posts/first.md', isTransient: false });
+  });
+
   it('initializes repository and refreshes repo state after clicking Initialize Git', async () => {
     const getRepoStateMock = vi
       .fn()
@@ -70,7 +158,7 @@ describe('GitSidebar', () => {
     });
 
     await vi.waitFor(() => {
-      expect(screen.getByText(/git repository ready/i)).toBeInTheDocument();
+      expect(screen.getByText(/open changes/i)).toBeInTheDocument();
     });
   });
 

tests/renderer/store/tabStore.test.ts

@@ -147,6 +147,40 @@ describe('Tab Management', () => {
       expect(getStore().tabs).toHaveLength(2);
       expect(getStore().activeTabId).toBe('post-1');
     });
+
+    it('should open git diff in a transient tab on single click', () => {
+      getStore().openTab({ type: 'git-diff', id: 'git-diff:posts/first.md', isTransient: true });
+
+      expect(getStore().tabs).toHaveLength(1);
+      expect(getStore().tabs[0]).toMatchObject({
+        type: 'git-diff',
+        id: 'git-diff:posts/first.md',
+        isTransient: true,
+      });
+    });
+
+    it('should reuse transient git diff tab on subsequent single click', () => {
+      getStore().openTab({ type: 'git-diff', id: 'git-diff:posts/first.md', isTransient: true });
+      getStore().openTab({ type: 'git-diff', id: 'git-diff:posts/second.md', isTransient: true });
+
+      expect(getStore().tabs).toHaveLength(1);
+      expect(getStore().tabs[0]).toMatchObject({
+        type: 'git-diff',
+        id: 'git-diff:posts/second.md',
+        isTransient: true,
+      });
+    });
+
+    it('should open git diff in a persistent tab on double click', () => {
+      getStore().openTab({ type: 'git-diff', id: 'git-diff:posts/first.md', isTransient: false });
+
+      expect(getStore().tabs).toHaveLength(1);
+      expect(getStore().tabs[0]).toMatchObject({
+        type: 'git-diff',
+        id: 'git-diff:posts/first.md',
+        isTransient: false,
+      });
+    });
   });
 
   describe('Closing Tabs', () => {

tests/setup.ts

@@ -48,6 +48,7 @@ Object.defineProperty(globalThis, 'window', {
         checkAvailability: vi.fn(),
         getRepoState: vi.fn(),
         getStatus: vi.fn(),
+        getDiff: vi.fn(),
         init: vi.fn(),
       },
       posts: {