Symfony Branch Cascade Merge

Merges each maintained branch into the next one, from oldest to newest.

Progress checklist

Step 0: Pre-flight checks
Step 1: Fetch maintained branches and pull them
Step 2: Cascade merge loop

Confirmation rule

Whenever the skill says "Wait for confirmation", treat anything other than an explicit affirmative as no: stop and ask the user how they want to proceed.

Step 0 — Pre-flight checks

bash

git status --porcelain --untracked-files=no

If any output, stop:

"The working tree is not clean. Please commit or stash your changes first."

Step 1 — Fetch maintained branches and pull them

1a. Get the branch list

bash

curl -s https://symfony.com/releases.json

Read maintained_versions. It is already sorted oldest → newest (e.g. ["6.4", "7.4", "8.0", "8.1"]). Store as BRANCHES.

1b. Pull every branch

For each branch in BRANCHES:

bash

git checkout <branch>
git pull --ff-only origin <branch>

Using --ff-only ensures local branches haven't diverged from origin. If the pull fails, stop and report the error.

Step 2 — Cascade merge loop

For each consecutive pair (SOURCE, TARGET) in BRANCHES:

2a. Merge

bash

git checkout <TARGET>
composer up
git merge <SOURCE>

Three outcomes are possible:

Already up-to-date: print "✓ <TARGET> already up-to-date with <SOURCE>" and skip to the next pair.
Clean merge (no conflicts): git creates the merge commit automatically. Proceed directly to step 2c.
Conflicts: proceed to step 2b.

2b. Resolve conflicts (only when git reports conflicts)

List conflicts:

bash

git diff --name-only --diff-filter=U

Read each conflicted file, resolve it, then git add it. When all are resolved:

bash

git commit --no-edit

Conflict resolution rules

File pattern	Strategy
`CHANGELOG*.md`	Keep entries from both sides; newer branch entries on top
Version constants, `composer.json` branch aliases	Keep the TARGET branch value
Code files	Merge logically based on context; when unsure, ask the user

Legacy tests across major versions

When merging from one major version to the next (e.g. 6.4 → 7.0), remove test methods marked with @group legacy or #[Group('legacy')]. The deprecations they cover have been removed in the new major version, so the tests are no longer relevant.

After resolving, show git diff HEAD~1 (first parent of the merge commit, i.e. the previous TARGET state) and wait for the user to confirm the resolution looks correct before proceeding.

2c. Run tests for affected components

Extract component, bridge, and bundle names from changed files:

bash

git diff --name-only HEAD~1..HEAD

Paths look like src/Symfony/{Component,Bridge,Bundle}/<NAME>/.... Deduplicate, then run tests for each:

bash

./phpunit src/Symfony/Component/<NAME>
./phpunit src/Symfony/Bridge/<NAME>
./phpunit src/Symfony/Bundle/<NAME>

For files under src/Symfony/Contracts/, run the single shared test suite:

bash

./phpunit src/Symfony/Contracts

Ignore files outside these directories (root configs, .github/, etc.): they don't have component-level test suites.

If tests fail or report PHPUnit deprecations (the PHPUnit version may differ between branches), first check whether the failure is pre-existing: run the same test on the TARGET branch before the merge (git stash && git checkout HEAD~1 or check CI). Only fix failures introduced by the merge:

Analyze and fix the code, including any PHPUnit deprecation notices.
Commit the fix: [<ComponentName>] Fix merge conflict resolution.
Re-run failing tests until green and deprecation-free.

Report any pre-existing failures to the user without attempting to fix them.

2d. Ask for confirmation before pushing

Show:

Merge: <SOURCE> → <TARGET>
Affected: <component list>
Tests: all passing

Commits since origin/<TARGET>:
git log --oneline origin/<TARGET>..<TARGET>

Ready to push? (yes / no)

Wait for confirmation. The user may make changes themselves before confirming.

2e. Push and continue

bash

git push origin <TARGET>

If the push fails, stop and report the error.

Print "✓ <SOURCE> → <TARGET> done." and continue to the next pair.

Final summary

All merges complete:
  6.4 → 7.4  ✓
  7.4 → 8.0  ✓
  8.0 → 8.1  ✓

Gotchas

CHANGELOG.md conflicts are the most common; entries must be kept from both sides, never dropped.
A merge can introduce test failures even without conflicts, because behavior from the older branch may be incompatible with newer code. Always run tests.
Some components have slow test suites. Only run tests for components with changed files, not the entire project.

Error handling

Never force-push or rewrite history.
Never use --no-verify on commits.
Never auto-recover from a failed git push or git pull. Stop and hand control back to the user.