takt: github-issue-398-branchexists (#401)

src/__tests__/clone.test.ts

@@ -570,6 +570,173 @@ describe('clone submodule arguments', () => {
   });
 });
 
+describe('branchExists remote tracking branch fallback', () => {
+  it('should clone with existing branch when only remote tracking branch exists', () => {
+    // Given: local branch does not exist, but origin/<branch> does
+    const cloneCalls: string[][] = [];
+    const checkoutCalls: string[][] = [];
+
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      // resolveBaseBranch: detectDefaultBranch
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref' && argsArr[2] === 'HEAD') {
+        return 'main\n';
+      }
+
+      // branchExists: git rev-parse --verify <branch>
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--verify') {
+        const ref = argsArr[2];
+        if (typeof ref === 'string' && ref.startsWith('origin/')) {
+          // Remote tracking branch exists
+          return Buffer.from('abc123');
+        }
+        // Local branch does not exist
+        throw new Error('branch not found');
+      }
+
+      if (argsArr[0] === 'clone') {
+        cloneCalls.push(argsArr);
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'checkout') {
+        checkoutCalls.push(argsArr);
+        return Buffer.from('');
+      }
+
+      return Buffer.from('');
+    });
+
+    // When
+    const result = createSharedClone('/project', {
+      worktree: '/tmp/clone-remote-branch',
+      taskSlug: 'remote-branch-task',
+      branch: 'feature/remote-only',
+    });
+
+    // Then: branch is the requested branch name
+    expect(result.branch).toBe('feature/remote-only');
+
+    // Then: cloneAndIsolate was called with --branch feature/remote-only (not base branch)
+    expect(cloneCalls).toHaveLength(1);
+    expect(cloneCalls[0]).toContain('--branch');
+    expect(cloneCalls[0]).toContain('feature/remote-only');
+
+    // Then: no checkout -b was called (branch already exists on remote)
+    expect(checkoutCalls).toHaveLength(0);
+  });
+
+  it('should create new branch when neither local nor remote tracking branch exists', () => {
+    // Given: neither local nor remote tracking branch exists
+    const cloneCalls: string[][] = [];
+    const checkoutCalls: string[][] = [];
+
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref' && argsArr[2] === 'HEAD') {
+        return 'main\n';
+      }
+
+      // Both local and remote tracking branch not found
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--verify') {
+        throw new Error('branch not found');
+      }
+
+      if (argsArr[0] === 'clone') {
+        cloneCalls.push(argsArr);
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'checkout') {
+        checkoutCalls.push(argsArr);
+        return Buffer.from('');
+      }
+
+      return Buffer.from('');
+    });
+
+    // When
+    const result = createSharedClone('/project', {
+      worktree: '/tmp/clone-no-branch',
+      taskSlug: 'no-branch-task',
+      branch: 'feature/brand-new',
+    });
+
+    // Then: branch is the requested branch name
+    expect(result.branch).toBe('feature/brand-new');
+
+    // Then: cloneAndIsolate was called with --branch main (base branch)
+    expect(cloneCalls).toHaveLength(1);
+    expect(cloneCalls[0]).toContain('--branch');
+    expect(cloneCalls[0]).toContain('main');
+
+    // Then: checkout -b was called to create the new branch
+    expect(checkoutCalls).toHaveLength(1);
+    expect(checkoutCalls[0]).toEqual(['checkout', '-b', 'feature/brand-new']);
+  });
+
+  it('should prefer local branch over remote tracking branch', () => {
+    // Given: local branch exists
+    const cloneCalls: string[][] = [];
+    const checkoutCalls: string[][] = [];
+
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref' && argsArr[2] === 'HEAD') {
+        return 'main\n';
+      }
+
+      // Local branch exists (first rev-parse --verify call succeeds)
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--verify') {
+        return Buffer.from('def456');
+      }
+
+      if (argsArr[0] === 'clone') {
+        cloneCalls.push(argsArr);
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'checkout') {
+        checkoutCalls.push(argsArr);
+        return Buffer.from('');
+      }
+
+      return Buffer.from('');
+    });
+
+    // When
+    const result = createSharedClone('/project', {
+      worktree: '/tmp/clone-local-branch',
+      taskSlug: 'local-branch-task',
+      branch: 'feature/local-exists',
+    });
+
+    // Then: cloneAndIsolate was called with --branch feature/local-exists
+    expect(result.branch).toBe('feature/local-exists');
+    expect(cloneCalls).toHaveLength(1);
+    expect(cloneCalls[0]).toContain('--branch');
+    expect(cloneCalls[0]).toContain('feature/local-exists');
+
+    // Then: no checkout -b was called (branch already exists locally)
+    expect(checkoutCalls).toHaveLength(0);
+  });
+});
+
 describe('autoFetch: true — fetch, rev-parse origin/<branch>, reset --hard', () => {
   it('should run git fetch, resolve origin/<branch> commit hash, and reset --hard in the clone', () => {
     // Given: autoFetch is enabled in global config.

src/infra/task/clone.ts

@@ -122,12 +122,23 @@ export class CloneManager {
   }
 
   private static branchExists(projectDir: string, branch: string): boolean {
+    // Local branch
     try {
       execFileSync('git', ['rev-parse', '--verify', branch], {
         cwd: projectDir,
         stdio: 'pipe',
       });
       return true;
+    } catch {
+      // not found locally — fall through to remote check
+    }
+    // Remote tracking branch
+    try {
+      execFileSync('git', ['rev-parse', '--verify', `origin/${branch}`], {
+        cwd: projectDir,
+        stdio: 'pipe',
+      });
+      return true;
     } catch {
       return false;
     }