# Git Control Specification

## Requirements

### Functional Requirements

1. **Branch Management**: Create, delete, list, and switch branches
2. **Working Directory**: View modified, added, deleted, and untracked files
3. **Commit Changes**: Stage and commit file changes with message
4. **Remote Sync**: Fetch, pull, and push to remote repositories
5. **Merge Branches**: Merge one branch into another
6. **Status Indicators**: Show file modification status in file tree

### Non-Functional Requirements

1. **Performance**: Git operations complete in < 3 seconds
2. **Feedback**: Show progress for long operations (push, pull, merge)
3. **Error Handling**: Clear error messages for all git failures
4. **Safety**: Confirm destructive operations (delete branch, force push)

## API Specification

### Branch Operations

#### POST /projects/{project_id}/repositories/{repo_id}/branches
Create a new branch.

**Request:**
```json
{
  "name": "feature/new-thing",
  "base_branch": "main"
}
```

**Response 201:**
```json
{
  "name": "feature/new-thing",
  "base_commit": "abc123"
}
```

**Response 400:** Branch already exists

#### DELETE /projects/{project_id}/repositories/{repo_id}/branches/{branch_name}
Delete a branch.

**Response 204:** Success

**Response 400:** Cannot delete current branch

#### POST /projects/{project_id}/repositories/{repo_id}/checkout
Checkout a branch.

**Request:**
```json
{
  "branch": "feature/new-thing"
}
```

**Response 200:**
```json
{
  "branch": "feature/new-thing",
  "commit": "abc123"
}
```

**Response 400:** Uncommitted changes

### Status Operations

#### GET /projects/{project_id}/repositories/{repo_id}/status
Get working directory status.

**Response 200:**
```json
{
  "branch": "main",
  "ahead": 2,
  "behind": 1,
  "modified": ["src/main.py"],
  "added": ["new-file.txt"],
  "deleted": [],
  "untracked": ["temp.log"],
  "renamed": []
}
```

### Commit Operations

#### POST /projects/{project_id}/repositories/{repo_id}/commits
Commit staged changes.

**Request:**
```json
{
  "message": "Update greeting",
  "author_name": "User",
  "author_email": "user@example.com"
}
```

**Response 201:**
```json
{
  "hash": "def789",
  "message": "Update greeting",
  "branch": "main"
}
```

**Response 400:** Nothing to commit

### Remote Operations

#### POST /projects/{project_id}/repositories/{repo_id}/fetch
Fetch from remote.

**Response 200:**
```json
{
  "success": true,
  "fetched_branches": ["origin/main", "origin/develop"]
}
```

#### POST /projects/{project_id}/repositories/{repo_id}/pull
Pull updates from remote.

**Request:**
```json
{
  "branch": "main"
}
```

**Response 200:**
```json
{
  "success": true,
  "commits": 3,
  "files_changed": ["src/main.py", "README.md"]
}
```

**Response 409:** Merge conflict

#### POST /projects/{project_id}/repositories/{repo_id}/push
Push to remote.

**Request:**
```json
{
  "branch": "main"
}
```

**Response 200:**
```json
{
  "success": true,
  "pushed_commits": 2
}
```

**Response 400:** Non-fast-forward

### Merge Operations

#### POST /projects/{project_id}/repositories/{repo_id}/merge
Merge branches.

**Request:**
```json
{
  "source_branch": "feature/new-thing",
  "target_branch": "main",
  "commit_message": "Merge feature into main"
}
```

**Response 200:**
```json
{
  "success": true,
  "commit_hash": "abc789",
  "files_changed": 5
}
```

**Response 409:** Merge conflict

## Data Model

### GitStatus
```typescript
interface GitStatus {
  branch: string;
  ahead: number;
  behind: number;
  modified: string[];
  added: string[];
  deleted: string[];
  untracked: string[];
  renamed: Array<{from: string, to: string}>;
}
```

### CommitInfo
```typescript
interface CommitInfo {
  hash: string;
  message: string;
  branch: string;
  author_name: string;
  author_email: string;
  date: string;
}
```

## Frontend Specification

### Components

**GitToolbar:**
- Fetch button
- Pull button (with behind count badge)
- Push button (with ahead count badge)
- Branch selector (with create/delete)
- Commit button (enabled when changes exist)
- Merge button

**BranchSelector:**
- Dropdown with all branches
- Current branch highlighted
- "Create new branch" option
- Delete option (with confirmation)

**CommitPanel:**
- Shows when files are modified
- Lists changed files with checkboxes
- Commit message input
- Commit button

**StatusIndicator:**
- Small badge on file tree items
- Shows modification type

### State Management

```typescript
interface GitControlState {
  status: GitStatus | null;
  isLoading: boolean;
  operations: Array<{
    type: string;
    status: 'pending' | 'success' | 'error';
    message: string;
  }>;
}
```

## Error Handling

| Error Code | Description | User Action |
|------------|-------------|-------------|
| DIRTY_WORKING_TREE | Uncommitted changes | Commit or stash changes |
| MERGE_CONFLICT | Merge failed with conflicts | Resolve conflicts manually |
| NON_FAST_FORWARD | Push rejected | Pull first |
| AUTH_FAILED | Remote auth failed | Check SSH keys |
| BRANCH_EXISTS | Branch already exists | Choose different name |
| NOTHING_TO_COMMIT | Working tree clean | N/A |
| CANNOT_DELETE_CURRENT | Can't delete checked out branch | Switch branches first |

## Testing Strategy

### Backend Tests
- Test branch creation/deletion
- Test checkout with/without changes
- Test commit operations
- Test fetch/pull/push
- Test merge (fast-forward and conflict)
- Test error cases

### Frontend Tests
- Test toolbar buttons
- Test branch selector
- Test commit panel
- Test status indicators
- Test error handling

### Integration Tests
- Full workflow: create branch → edit file → commit → push → merge