# Git Control - Design

## Architecture

```
Repository Workspace
├─ Toolbar
│  ├─ [Fetch] [Pull] [Push]
│  ├─ [Branch: main ▼] [+ New Branch]
│  └─ [Commit] [Merge ▼]
├─ Sidebar
│  ├─ Repo Selector
│  ├─ Branch Selector (with management)
│  └─ File Tree (with status icons)
│     ├─ 📄 main.py ✏️ (modified)
│     ├─ 📁 src/
│     └─ 📄 README.md ✨ (new)
└─ Main Content
   ├─ File Viewer (with edit/save)
   └─ Commit Panel (when files modified)
      ├─ Changed files list
      ├─ Commit message input
      └─ [Commit to main] button
```

## Git Operations

### Branch Operations

**Create Branch:**
```
POST /projects/{id}/repositories/{id}/branches
{
  "name": "feature/new-thing",
  "base_branch": "main"
}
```

**Delete Branch:**
```
DELETE /projects/{id}/repositories/{id}/branches/{name}
```

**Checkout Branch:**
```
POST /projects/{id}/repositories/{id}/checkout
{
  "branch": "feature/new-thing"
}
```

### Working Directory Status

**Get Status:**
```
GET /projects/{id}/repositories/{id}/status
```

Response:
```json
{
  "branch": "main",
  "modified": ["src/main.py", "README.md"],
  "added": ["new-file.txt"],
  "deleted": ["old-file.txt"],
  "untracked": ["temp.log"]
}
```

### Commit Operations

**Commit Changes:**
```
POST /projects/{id}/repositories/{id}/commits
{
  "message": "Update greeting",
  "author_name": "User",
  "author_email": "user@example.com",
  "files": ["src/main.py", "README.md"]
}
```

### Remote Operations

**Fetch:**
```
POST /projects/{id}/repositories/{id}/fetch
```

**Pull:**
```
POST /projects/{id}/repositories/{id}/pull
{
  "branch": "main",
  "strategy": "merge"
}
```

**Push:**
```
POST /projects/{id}/repositories/{id}/push
{
  "branch": "main"
}
```

**Merge:**
```
POST /projects/{id}/repositories/{id}/merge
{
  "source_branch": "feature/new-thing",
  "target_branch": "main",
  "commit_message": "Merge feature into main"
}
```

## Backend Implementation

### Git Command Utilities

Extend `src/utils/git_files.py` with:
- `get_status(repo_path)` - working directory status
- `create_branch(repo_path, name, base)` - create new branch
- `delete_branch(repo_path, name)` - delete branch
- `checkout_branch(repo_path, name)` - switch branch
- `commit_changes(repo_path, files, message, author)` - commit files
- `fetch(repo_path)` - fetch from remote
- `pull(repo_path, branch)` - pull updates
- `push(repo_path, branch)` - push changes
- `merge(repo_path, source, target, message)` - merge branches

### Error Handling

All git operations can fail:
- **Merge conflicts**: Return conflict details, require resolution
- **Auth failures**: Remote requires authentication
- **Dirty working tree**: Can't checkout with uncommitted changes
- **Branch exists**: Can't create duplicate branch
- **Nothing to commit**: Working tree clean

### Security

- All operations check repository ownership
- Push/pull requires valid remote URL
- Commits use authenticated user's identity

## Frontend Implementation

### Workspace Toolbar

Add git action bar above file viewer:
```
┌──────────────────────────────────────────────────────┐
│ [Fetch] [Pull] [Push]  │  Branch: [main ▼] [+ New] │
│                        │  [Commit ▼] [Merge ▼]      │
└──────────────────────────────────────────────────────┘
```

### Branch Management

**Branch Selector Dropdown:**
- List all branches with current branch highlighted
- Create new branch option (opens dialog)
- Delete branch option (with confirmation)

**New Branch Dialog:**
```
┌──────────────────────────────┐
│ Create New Branch            │
├──────────────────────────────┤
│ Name: [feature/________]     │
│ Base: [main ▼]               │
│                              │
│ [Create] [Cancel]            │
└──────────────────────────────┘
```

### Working Directory Status

**Status Indicators in File Tree:**
- ✏️ Modified file
- ✨ New file
- 🗑️ Deleted file
- ❓ Untracked file

**Commit Panel (appears when files modified):**
```
┌──────────────────────────────┐
│ Changes (3)                  │
├──────────────────────────────┤
│ ✏️ src/main.py               │
│ ✨ new-file.txt              │
│ 🗑️ old-file.txt             │
├──────────────────────────────┤
│ Commit message:              │
│ [____________________]       │
│                              │
│ [Commit to main]             │
└──────────────────────────────┘
```

### Merge Dialog

```
┌──────────────────────────────┐
│ Merge Branch                 │
├──────────────────────────────┤
│ Source: [feature/xyz ▼]      │
│ Target: main                 │
│                              │
│ Commit message:              │
│ [Merge feature/xyz into main]│
│                              │
│ [Merge] [Cancel]             │
└──────────────────────────────┘
```

## Implementation Order

1. **Backend git utilities** - Status, branch, commit, remote operations
2. **Backend API endpoints** - All git operation endpoints
3. **Frontend toolbar** - Git action buttons
4. **Frontend branch management** - Create/delete/checkout
5. **Frontend status display** - Modified file indicators
6. **Frontend commit panel** - Commit UI
7. **Frontend merge dialog** - Merge UI
8. **Integration** - Wire everything together
9. **Tests** - Backend + frontend tests

## State Management

### URL State
```
/projects/:projectId?repo=:repoId&branch=:branch&path=:path
```

### React State
```typescript
interface GitState {
  currentBranch: string;
  branches: Branch[];
  status: {
    modified: string[];
    added: string[];
    deleted: string[];
    untracked: string[];
  };
  isLoading: boolean;
  lastOperation: string | null;
}
```

## Error Handling

### User-Facing Errors
- **"Cannot checkout: uncommitted changes"** - Show commit panel
- **"Merge conflict"** - Show conflict resolution UI
- **"Push rejected: non-fast-forward"** - Suggest pull first
- **"Authentication failed"** - Show SSH key settings
- **"Nothing to commit"** - Working tree clean

### Conflict Resolution (Future)
For now, show error and abort. Later can add:
- Diff view of conflicts
- Manual resolution editor
- Accept ours/theirs buttons

## Performance Considerations

- **Status updates**: Poll every 5 seconds when viewing workspace
- **Fetch on load**: Auto-fetch when opening workspace (optional)
- **Lazy operations**: Don't fetch until user clicks fetch/pull
- **Progress indicators**: Show for long operations (clone, push, merge)