workflow-preflight

What this skill does

# /workflow:preflight

Pre-work validation to prevent wasted effort from stale state, redundant work, or branch conflicts.

## When to Use This Skill

| Use this skill when... | Skip when... |
|------------------------|-------------|
| Starting work on a new issue or feature | Quick single-file edit |
| Resuming work after a break | Already verified state this session |
| Before spawning parallel agents | Working in an isolated worktree |
| Before creating a branch for a PR | Branch already created and verified |

## Context

- Repo: !`git remote get-url origin`
- Current branch: !`git branch --show-current`
- Remote tracking: !`git branch -vv --format='%(refname:short) %(upstream:short) %(upstream:track)'`
- Uncommitted changes: !`git status --porcelain`
- Stash count: !`git stash list`

## Execution

### Step 1: Fetch Latest Remote State

```bash
git fetch origin --prune 2>/dev/null
```

### Step 2: Check for Existing Work

If an issue number was provided, check if it's already addressed:

```bash
# Check if issue exists and its state
gh issue view $ISSUE --json number,title,state,labels 2>/dev/null

# Check for PRs that reference this issue
gh pr list --search "fixes #$ISSUE OR closes #$ISSUE OR resolves #$ISSUE" --json number,title,state,headRefName 2>/dev/null

# Check for branches that reference this issue
git branch -a --list "*issue-$ISSUE*" --list "*fix/$ISSUE*" --list "*feat/$ISSUE*" 2>/dev/null
```

**If a merged PR exists**: Report that the issue is already addressed. Stop.
**If an open PR exists**: Report the PR and ask if the user wants to continue on that branch or start fresh.

### Step 3: Verify Branch State

```bash
# Check divergence from main/master
git log --oneline origin/main..HEAD 2>/dev/null || git log --oneline origin/master..HEAD 2>/dev/null

# Check if main has moved ahead
git log --oneline HEAD..origin/main -5 2>/dev/null || git log --oneline HEAD..origin/master -5 2>/dev/null

# Check for uncommitted changes
git status --porcelain=v2 --branch 2>/dev/null
```

**Report**:
- Commits ahead/behind remote
- Uncommitted changes that might interfere
- Whether a rebase is needed

### Step 4: Check for Conflicts

```bash
# Dry-run merge to detect conflicts (without actually merging)
git merge-tree $(git merge-base HEAD origin/main) HEAD origin/main 2>/dev/null | head -20
```

### Step 5: Summary Report

Output a structured summary:

| Check | Status | Detail |
|-------|--------|--------|
| Remote state | fresh/stale | Last fetch time |
| Existing PRs | none/open/merged | PR numbers if any |
| Branch state | clean/dirty/diverged | Ahead/behind counts |
| Conflicts | none/detected | Conflicting files |
| Stash | empty/N items | Stash contents |

**Recommendations**:
- If behind remote: "Rebase recommended before starting work"
- If existing PR found: "PR #N already addresses this - review before duplicating"
- If dirty state: "Commit or stash changes before branching"
- If conflicts detected: "Resolve conflicts with main before proceeding"
- If clean: "Ready to proceed"

## Agentic Optimizations

| Context | Command |
|---------|---------|
| Quick remote sync | `git fetch origin --prune 2>/dev/null` |
| Check existing PRs | `gh pr list --search "fixes #N" --json number,state,headRefName` |
| Branch divergence | `git log --oneline origin/main..HEAD` |
| Conflict detection | `git merge-tree $(git merge-base HEAD origin/main) HEAD origin/main` |
| Compact status | `git status --porcelain=v2 --branch` |
| Remote tracking | `git branch -vv --format='%(refname:short) %(upstream:track)'` |

## Quick Reference

| Flag | Description |
|------|-------------|
| `git fetch --prune` | Fetch and remove stale remote refs |
| `git status --porcelain=v2` | Machine-parseable status |
| `gh pr list --search` | Search PRs by content |
| `gh issue view --json` | Structured issue data |
| `git merge-tree` | Dry-run merge conflict detection |
| `git log A..B` | Commits in B but not A |