msd-core/docs/branching.md

Branching Model

A plain-English guide to where work happens, where it merges, and why you should almost never need to rebase.

Audience: maintainers and contributors. Aimed at people who can use git but don't want to think about it every day. If you came up through CIS in the late 90s and never quite warmed to git's mental model — this guide is for you.

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TL;DR

                    feat/NNN-slug ─┐
                    fix/NNN-slug  ─┤
                    chore/NNN-slug ┼──► next (integration) ──► release/X.Y.0 ──► main ──► v-tag ──► npm @latest
                    docs/NNN-slug ─┘                                      │
                                                                          │
                    hotfix/X.Y.Z ◄── branch from v-tag ──────┐            │
                                  cherry-pick from next ─────┤            │
                                  ──────────────────────────►│──► main ──►v-tag (patch) ──► npm @latest
                                                              │            │
                                                              └─► next  ◄──┘ (auto back-merge)

Three rules:

1. You PR to next. Not main. Unless you're cutting a release or a hotfix, the answer to "where does my PR go?" is always next.
2. main only moves on release. Maintainers (and the release/hotfix workflows) push to main. Feature work never touches it.
3. Hotfixes go to main first, then auto-merge back to next. Urgent fixes don't wait for the release train.

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The two long-lived branches

main — production

• Represents what's on npm @latest right now.
• Only changes when a release lands, a hotfix lands, or — rarely — when an emergency fix is cherry-picked.
• Tagged with vX.Y.Z on every release.
• Branch protection: 2 approvals, CI green, signed commits, linear history not required (release back-merges use merge commits to preserve tag context).
• Never push directly. Even maintainers go through PRs.

next — integration for the next release

• Represents what will be in the next minor or major release.
• This is where day-to-day feature, fix, chore, docs, and refactor work lands.
• Always at-or-ahead of main: contains everything in main plus everything queued for the next release.
• Branch protection: 1 approval, CI green, auto-deleted source branches.
• Auto-back-merged from main whenever main advances (via auto-backmerge.yml) so it never falls behind.

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Short-lived branches

These are work branches. Open one, push commits, PR it, merge it, let it auto-delete.

Prefix	What it's for	PR target	Examples
feat/	New feature (approved-feature issue)	next	feat/3201-discuss-mode
fix/	Bug fix (confirmed-bug issue)	next	fix/3187-config-corruption
chore/	Maintenance, refactors, deps, CI	next	chore/3712-bump-node-actions
docs/	Documentation only	next	docs/3485-adr-naming-convention
refactor/	Internal restructuring, no behavior change	next	refactor/3500-extract-seam
test/	Test-only additions or corrections	next	test/3621-restore-fixture
perf/	Performance work, no behavior change	next	perf/3300-skill-index
ci/	CI/workflow changes only	next	ci/3801-add-node-26-matrix
revert/	Reverting a previously-merged change	next (or main if urgent)	revert/3919-bad-merge
hotfix/X.Y.Z	Patch release branch (created by release.yml with a patch version X.Y.Z)	main	hotfix/1.27.1
release/X.Y.0	Minor/major release branch (created by release.yml)	main	release/1.28.0

The branch name rule is enforced by .github/workflows/branch-naming.yml. A PR from a non-conforming branch gets a warning comment. Pick a prefix.

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Three flows: feature, hotfix, release

Flow 1 — Feature / fix / chore (the 95% case)

This is what you do every day.

# 1. Start from a fresh `next`.
git fetch origin
git checkout next
git pull --ff-only origin next

# 2. Branch off `next`.
git checkout -b fix/3187-config-corruption

# 3. Work. Commit. Push.
git add -A && git commit -m "fix: harden config parse for trailing comma"
git push -u origin fix/3187-config-corruption

# 4. Open a PR. Target = next. (Don't change the target.)
gh pr create --base next --repo open-gsd/gsd-core

# 5. CI runs. Reviewer approves. PR squash-merges into `next`.
#    Your branch auto-deletes.

Why this rarely needs a rebase:

• next moves slower than main did in the old single-branch model — only changes when other PRs to next merge.
• Branch protection on next does not require "up-to-date before merge" — only requires CI to be green. So another PR landing on next while yours is open doesn't force you to rebase.
• Squash-merge means each PR becomes one commit on next — easy to revert, easy to read, no merge-noise.

Flow 2 — Hotfix (urgent patch release)

When you need to ship a fix without waiting for the next minor.

# 1. The fix itself lands on `next` first (or main, for true emergencies).
#    Open the PR exactly like a normal fix.
git checkout next
git pull --ff-only
git checkout -b fix/3919-critical-crash
# ... commit, push, PR to next, merge.

# 2. Trigger the Release workflow (release.yml) from the Actions tab:
#    workflow:  Release
#    action:    create
#    version:   1.27.1   (next patch number, X.Y.Z)
#    auto_cherry_pick: true (default)

The workflow:

1. Finds the prior tag (v1.27.0) — the cherry-pick base.
2. Creates hotfix/1.27.1 from that tag.
3. Cherry-picks every fix: / chore: commit on next (or main) that isn't already in v1.27.0, oldest-first.
4. Bumps versions, pushes the branch.
5. You review the branch. Trigger finalize when ready.
6. finalize publishes to npm @latest, tags v1.27.1, opens merge-back PRs to both main and next.

See .github/workflows/release.yml and VERSIONING.md for the deep dive.

Flow 3 — Minor or major release

When next has accumulated enough work to ship a new minor/major.

1. Maintainer triggers Actions → Release workflow:
   - action: create
   - version: 1.28.0

2. Workflow cuts release/1.28.0 from `next` (not main).
   `next` keeps moving — new feature PRs can target it.

3. Stabilization on release/1.28.0:
   - Bug fixes can be PR'd to release/1.28.0 directly (`fix/3923-rc-blocker`)
   - Each fix should also be PR'd to `next` so the next release has it too
     (or wait for the auto-back-merge after finalize)
   - Trigger `rc` action to publish RC builds: 1.28.0-rc.1, rc.2, ...
   - Each `rc` run also prints a non-destructive preview of the curated `## [X.Y.0]` CHANGELOG section in the Actions job summary — rendered from the `.changeset/` fragments without consuming them — so you can review the upcoming release notes during RC testing.

4. When stable: trigger `finalize`.
   - Publishes to npm @latest
   - Tags v1.28.0
   - Opens merge-back PR: release/1.28.0 → main
   - Opens merge-back PR: release/1.28.0 → next (NEW — picks up RC-only fixes)

5. Merge both back-merge PRs. release/1.28.0 branch is deleted.

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Why this fixes the "constant rebase" pain

The old single-branch model:

• Every PR targets main.
• main moves every time anything lands.
• Branch protection often requires "branches up to date" — so the moment someone else's PR merges, your PR demands a rebase before it can merge.
• 10 PRs in flight = 9 of them need to rebase every time one lands. The last one to merge has rebased N times.

The new model removes the pressure in three ways:

1. main rarely moves. Only release/hotfix merges land. Most days main doesn't change at all.
2. next does NOT require "up-to-date before merge". Branch protection on next only requires CI green. Two PRs to next can merge in either order without rebasing each other — git will handle the merge as long as they don't touch the same lines.
3. Squash-merge into next. One commit per PR. No "merge main into my branch" noise. If you ever do need to bring next into your branch (because of a real conflict), it's one rebase per conflict, not per PR that lands somewhere else.

You'll still occasionally rebase — when your branch genuinely conflicts with something that landed on next. But that's a real conflict you'd have to resolve anyway. The treadmill is gone.

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Cheat sheet: "where does my PR go?"

Is it a hotfix release branch?       → main      (cut by release.yml with a patch version X.Y.Z)
Is it a stable release branch?       → main      (cut by release.yml)
Is it an RC-blocker fix?             → release/X.Y.0  (and also next, or rely on back-merge)
Is it everything else?               → next

If you're unsure: next. The PR target validator (pr-target-validator.yml) will reject PRs that target main from non-release/hotfix branches and tell you to retarget. Use the GitHub UI "Edit" button on the PR title to change the base branch — no need to recreate the PR.

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Maintainer reference

• First-time bootstrap: run scripts/setup-branch-protection.sh after creating the next branch for the first time. It applies protection rules to both main and next consistently.
• Repo Settings → General → Pull Requests:
  • Allow squash merging — ON (default merge strategy)
  • Allow merge commits — ON (needed for release/hotfix back-merges)
  • Allow rebase merging — OFF (avoids confusion)
  • Default to "Pull request title" for squash commit messages — ON
  • Automatically delete head branches — ON
  • Allow auto-merge — ON (the auto-backmerge workflow uses it)
• Creating next for the first time:

  git checkout main
  git pull --ff-only
  git checkout -b next
  git push -u origin next
  # Then go to repo Settings → Branches and set `next` as the default branch
  # (so `gh pr create` and the GitHub web UI default to it).
  

• Phasing in: see the migration notes in docs/adr/230-introduce-next-integration-branch.md.
• Updating release.yml: this workflow currently branches from main and cherry-picks from main. After phase-2 of the migration it should branch from next (release) and cherry-pick from next (hotfix). The patches are inlined in the ADR.

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When NOT to use next

A few exceptions where the rules above bend:

• True production-down emergency. Push directly to a fix/critical-* branch, PR to main. The auto-back-merge workflow will replay it onto next within minutes. Use sparingly — most "urgent" things are fine to go through next and ship same day via the Release workflow (patch version).
• Documentation-only typo on a published page. If the only change is a doc fix that's visible right now and shouldn't wait for the next release, PR it to main. The auto-back-merge will sync next. Most doc changes should still go through next and ship with the next release.
• CI / workflow files. Strictly speaking these affect the repo state, not the published artifact. They can target next or main. Convention: PR to next unless the CI fix unblocks a release in progress.