rebase-to-upstream

Rebase To Upstream

Use this skill when the current local branch should be replayed onto upstream/main.

upstream/main is the default target, but the same process should work with any provided remote branch such as origin/main or upstream/release.

Task List

- [ ] Inspect the current branch, target branch, and local changes
- [ ] Stash local changes if needed
- [ ] Create a backup branch before resetting
- [ ] Reset the current branch to the target ref (e.g., upstream/main)
- [ ] Cherry-pick missing commits from the backup branch one by one
  - For each commit with conflicts: resolve source, then manifests, then lockfiles
  - For package.json conflicts: compare each dependency individually and keep the highest semantic version (e.g., 11.11.1 > 11.11.0, 21.2.0 > 20.3.2)
  - After resolving lockfile conflicts: regenerate via wrapper before committing
- [ ] Re-apply any stash and resolve conflicts with the same rules
- [ ] Delete the backup branch
- [ ] Run validation and summarize the final branch state

Workflow

1. Inspect Current State

TARGET_REF=${TARGET_REF:-upstream/main}
CURRENT_BRANCH=$(git branch --show-current)
BACKUP_BRANCH="backup/${CURRENT_BRANCH//\//-}"

git fetch --all --prune
printf '%s\n' "$CURRENT_BRANCH"
git status --short
git log --oneline --decorate --graph --max-count=20

2. Stash if Needed, Then Create a Backup

Only stash if there are actual local changes:

# Check for changes first
git status --short

# Only if the output is not empty
git stash push -u -m "rebase-to-upstream: $CURRENT_BRANCH"

# Always create a backup branch before any destructive operation.
git branch "$BACKUP_BRANCH"

3. Reset to Target

git reset --hard "$TARGET_REF"

4. Identify Missing Commits

git cherry -v "$TARGET_REF" "$BACKUP_BRANCH"
git log --reverse --cherry-pick --right-only --format=%H "$TARGET_REF...$BACKUP_BRANCH"

5. Cherry-Pick Commits One by One

For each commit:

git cherry-pick <commit-hash>

If conflicts occur, resolve them in this order:

Step 5a: Resolve Source Files

• Resolve using standard merge conflict resolution
• Stage resolved files: git add <path>

Step 5b: Resolve Manifests (package.json)

• Compare both sides dependency-by-dependency (not block-by-block)
• For each dependency key, resolve versions using semantic version comparison:
  • Parse versions as major.minor.patch (ignore pre-release tags like -alpha, -beta)
  • Compare major first, then minor, then patch
  • Keep the highest version number for that specific dependency
• Examples:
  • "npm": "11.11.0" vs "npm": "11.11.1" → keep 11.11.1 (patch is higher)
  • "ng-packagr": "20.3.2" vs "ng-packagr": "21.2.0" → keep 21.2.0 (major is higher)
  • "rxjs": "7.8.0" vs "rxjs": "7.5.0" → keep 7.8.0 (minor is higher)
• CRITICAL: Do NOT use git checkout --theirs or git checkout --ours for package.json conflicts. These commands accept/reject the entire conflict block, which will incorrectly resolve some dependencies. You must manually edit the file to keep the highest version for each individual dependency.
• Stage resolved files: git add <path>

Step 5c: Resolve Lockfiles (package-lock.json)

• Do NOT manually edit or merge conflict markers

• Accept the cherry-picked side: git checkout --theirs path/to/package-lock.json

• Regenerate immediately via wrapper before committing:

  # Standard flow: just run npm install via wrapper for affected project.
  COMPOSE_PROJECT_NAME=ngmocks_rebase_<unique> sh compose.sh <affected-target>
  
  # Only if npm install fails, use the update workaround:
  # 1) Edit compose.yml: change service command from "npm install" to "npm update"
  # 2) Run: COMPOSE_PROJECT_NAME=ngmocks_rebase_<unique> sh compose.sh <affected-target>
  # 3) Restore compose.yml back to "npm install --no-audit"
  # 4) Run: COMPOSE_PROJECT_NAME=ngmocks_rebase_<unique> sh compose.sh <affected-target>
  

• Stage the regenerated lockfile: git add path/to/package-lock.json

Step 5d: Complete the Cherry-Pick

git cherry-pick --continue
# Or if no auto-commit: git commit --no-verify -m "original commit message"

6. Apply Stash (if one was created)

git stash list
git stash apply <stash-ref>

# If conflicts occur, resolve using the same rules as step 5
# Regenerate lockfiles via wrapper before committing if needed

7. Cleanup

git branch -d "$BACKUP_BRANCH"
# If rebased commit hashes make the safe delete fail, inspect the output first:
git cherry -v HEAD "$BACKUP_BRANCH"
# Delete forcibly only after every listed commit is marked `-`.
git branch -D "$BACKUP_BRANCH"

8. Validation

Run validation for affected targets:

COMPOSE_PROJECT_NAME=ngmocks_rebase_<unique> sh test.sh <affected-target> # For specific project/suite changes
COMPOSE_PROJECT_NAME=ngmocks_rebase_<unique> sh test.sh root # Only when root files changed
COMPOSE_PROJECT_NAME=ngmocks_rebase_<unique> sh test.sh e2e # Only when tests-e2e or shared e2e files changed

Conflict Resolution Quick Reference

When conflicts occur during cherry-pick, resolve in this order:

1. Source files: Standard merge resolution
2. package.json: Manual edit per dependency (see Step 5b)
3. package-lock.json: git checkout --theirs then regenerate via wrapper (see Step 5c)

Guardrails

• This skill is branch-agnostic: works from any current local branch
• upstream/main is only the default target; override when user provides another remote branch
• Always create backup branch before git reset --hard
• Only stash when local changes actually exist (check with git status --short)
• Use repo wrappers (sh compose.sh, sh test.sh) for all npm operations; never run ad-hoc local npm install or npm update
• Use a unique COMPOSE_PROJECT_NAME whenever another worktree or agent session may be active.
• Regenerate lockfiles immediately after resolving conflicts, before committing each cherry-pick - this keeps each commit atomic and correct