merge-strategy

# Merge Strategy Configuration

This skill covers sidecar's git merge and pull operations, their current implementation, known gaps, and recommended configuration patterns.

## Current Implementation

### Git Status Plugin Pull Strategies

Location: `internal/plugins/gitstatus/pull_menu.go`, `internal/plugins/gitstatus/remote.go`

The git-status plugin offers four pull strategies via a modal menu:

| Strategy | Command | Use Case |
|----------|---------|----------|
| Pull (merge) | `git pull` | Creates merge commit, preserves branch topology |
| Pull (rebase) | `git pull --rebase` | Replays local commits on top of upstream |
| Pull (fast-forward only) | `git pull --ff-only` | Only pulls if fast-forward possible (safest) |
| Pull (rebase + autostash) | `git pull --rebase --autostash` | Rebase with automatic stash/unstash |

### Workspace Plugin Merge Workflows

Location: `internal/plugins/workspace/merge.go`

**PR Workflow:**
1. Push branch to remote
2. Create PR via `gh pr create`
3. Wait for PR merge (polling)
4. Cleanup: delete worktree, branches, pull base

**Direct Merge (No PR)** at `merge.go:430-498`:
```
1. git fetch origin <baseBranch>
2. git checkout <baseBranch>
3. git pull origin <baseBranch>
4. git merge <branch> --no-ff -m "Merge branch '<branch>'"  // Hardcoded --no-ff
5. git push origin <baseBranch>
```

**Post-Merge Pull** at `merge.go:500-551`:
- When on base branch: `git pull --ff-only origin <branch>` (hardcoded)
- Otherwise: `git fetch` + `git update-ref`

**Divergence Resolution** at `merge.go:644-705`:
- Rebase option: `git pull --rebase origin <branch>`
- Merge option: `git pull origin <branch>`

## Known Issues and Gaps

1. **No configurable defaults** -- users must select strategy every time
2. **Limited merge strategies** -- direct merge hardcoded to `--no-ff`, missing `--ff`, `--ff-only`, `--squash`, rebase-based integration
3. **No squash merge support** -- no clean-history option for main branch
4. **Hardcoded commit messages** -- `fmt.Sprintf("Merge branch '%s'", branch)`, no templates
5. **Missing safety options** -- no GPG signing, no `--verify-signatures`, no `--force-with-lease`
6. **Autostash inconsistency** -- available for pull-rebase but not post-merge pull or divergence resolution
7. **No upstream tracking config** -- remote always `origin`, no configurable tracking
8. **Limited conflict recovery** -- only abort or dismiss, no continue/skip rebase
9. **No interactive rebase** -- no squash/reorder/edit before merge

## Recommended Configuration Schema

Add to `internal/config/config.go`:

```go
type GitConfig struct {
    DefaultPullStrategy  string   `json:"defaultPullStrategy,omitempty"`  // "merge", "rebase", "ff-only", "autostash"
    DefaultMergeStrategy string   `json:"defaultMergeStrategy,omitempty"` // "no-ff", "ff", "ff-only", "squash", "rebase"
    MergeCommitTemplate  string   `json:"mergeCommitTemplate,omitempty"`  // Go template: .Branch, .BaseBranch, .PRTitle, .PRNumber
    SignCommits          bool     `json:"signCommits,omitempty"`
    SignMerges           bool     `json:"signMerges,omitempty"`
    AutostashOnPull      bool     `json:"autostashOnPull,omitempty"`
    DefaultRemote        string   `json:"defaultRemote,omitempty"`        // Default: "origin"
    SetUpstreamOnPush    bool     `json:"setUpstreamOnPush,omitempty"`
    ProtectedBranches    []string `json:"protectedBranches,omitempty"`    // e.g. ["main", "master", "release/*"]
    PreMergeChecks       []string `json:"preMergeChecks,omitempty"`       // e.g. ["go test ./..."]
}
```

Add to `PluginsConfig`:
```go
type PluginsConfig struct {
    Git       GitConfig             `json:"git"`
    GitStatus GitStatusPluginConfig `json:"git-status"`
    // ... existing fields
}
```

Example user config (`~/.config/sidecar/config.json`):
```json
{
  "plugins": {
    "git": {
      "defaultPullStrategy": "rebase",
      "defaultMergeStrategy": "squash",
      "mergeCommitTemplate": "Merge {{.Branch}} into {{.BaseBranch}}",
      "signCommits": true,
      "autostashOnPull": true,
      "protectedBranches": ["main", "production"]
    }
  }
}
```

## Implementation Priorities

### Priority 1: Default Pull Strategy

**Files:** `internal/config/config.go`, `internal/plugins/gitstatus/pull_menu.go`, `internal/plugins/gitstatus/update_handlers.go`

- If `defaultPullStrategy` is set, execute directly (skip menu)
- If unset, show menu as today
- Consider adding "Always use this" option to menu

### Priority 2: Default Merge Strategy

**File:** `internal/plugins/workspace/merge.go` -- `performDirectMerge()`

```go
func (p *Plugin) performDirectMerge(wt *Worktree) tea.Cmd {
    strategy := p.ctx.Config.Plugins.Git.DefaultMergeStrategy
    if strategy == "" {
        strategy = "no-ff" // backward compatible default
    }
    var mergeArgs []string
    switch strategy {
    case "ff":
        mergeArgs = []string{"merge", branch, "-m", mergeMsg}
    case "ff-only":
        mergeArgs = []string{"merge", branch, "--ff-only"}
    case "squash":
        mergeArgs = []string{"merge", branch, "--squash"}
    case "rebase":
        // 1. git rebase baseBranch branch
        // 2. git checkout baseBranch
        // 3. git merge branch --ff-only
    default: // "no-ff"
        mergeArgs = []string{"merge", branch, "--no-ff", "-m", mergeMsg}
    }
}
```

### Priority 3: Squash Merge Support

After `git merge --squash`, a separate commit is needed:
```go
case "squash":
    mergeCmd := exec.Command("git", "merge", branch, "--squash")
    // execute...
    commitMsg := fmt.Sprintf("Squash merge branch '%s'", branch)
    commitCmd := exec.Command("git", "commit", "-m", commitMsg)
```

### Priority 4: Merge Commit Templates

```go
type MergeTemplateData struct {
    Branch, BaseBranch, PRTitle, PRNumber string
}

func renderMergeMessage(tmpl string, data MergeTemplateData) (string, error) {
    if tmpl == "" {
        tmpl = "Merge branch '{{.Branch}}'"
    }
    t, err := template.New("merge").Parse(tmpl)