Support --allow-merge-commits flag to skip validation of merge commits

[bagowix]

Hi!
Currently, conventional-pre-commit fails on merge commits because their commit messages (like Merge branch 'master' into feature/my-branch) do not follow the Conventional Commits standard.

It would be very useful to have an option like --allow-merge-commits to skip validation of merge commits automatically.

Use Case:

• Developers merging master or other branches into feature branches.
• CI pipelines where automatic merges happen.
• Keeping history clean without manually editing merge commit messages.

Proposal:

• Add a flag --allow-merge-commits.
• If this flag is set, conventional-pre-commit should skip validation for commits that start with Merge ....
• Ideally, detection could be done by checking if the commit message starts with Merge or using Git’s metadata.

Why it’s important:

• Merge commits are common in many workflows.
• Developers are forced to rewrite merge commit messages manually, which can break Git history clarity or cause frustration.

[thekaveman]

Thanks for the detailed write-up @bagowix.

What version of conventional-pre-commit are you using? Since the latest version (v4.0.0, December 2024) the default behavior is to skip checking merge commits, meaning there is no need for a flag.

The --strict flag can be used to disallow merge commits and e.g. fixup! style commits. But otherwise, these are allowed by default.

[bagowix]

Hi, thanks again for the quick response!

I’m actually using conventional-pre-commit version v4.0.0, but I’m still consistently encountering this issue.
When I perform a regular merge (like merging master into my feature branch), the pre-commit hook blocks the commit with an error about a bad commit message, even though it’s a standard merge message.

  - repo: https://github.com/compilerla/conventional-pre-commit
    rev: v4.0.0
    hooks:
      - id: conventional-pre-commit
        stages: [commit-msg]
        args: [--verbose]

Here’s an example of the error I get:

Conventional Commit......................................................Failed
- hook id: conventional-pre-commit
- exit code: 1
[Bad commit message] >> Merge remote-tracking branch 'refs/remotes/origin/master' into feat/*****
Your commit message does not follow Conventional Commits formatting
https://www.conventionalcommits.org/
Conventional Commit messages follow a pattern like:
    type(scope): subject
    extended body
Please correct the following errors:
  - Expected value for type from: build, chore, ci, docs, feat, fix, perf, refactor, revert, style, test
Run:
    git commit --edit --file=.git/COMMIT_EDITMSG
to edit the commit message and retry the commit.
Not committing merge; use 'git commit' to complete the merge.

It seems like merge commits are still being validated.
Maybe there’s a configuration or usage detail I’m missing?

Would appreciate any advice or suggestions! Thanks again!

[thekaveman]

Ah, thank you for sharing the error output, that was helpful! I think I see the issue:

[Bad commit message] >> Merge remote-tracking branch 'refs/remotes/origin/master' into feat/*****

We check for commit messages that start with "Merge branch", which of course doesn't work for your use-case of merging a remote branch. Sorry for this oversight!

I would happily accept a PR (with tests) to fix this.

[bagowix]

I’d be happy to jump in and fix this!

[thekaveman]

Thanks again @bagowix! This fix is now released in v4.1.0:

• https://github.com/compilerla/conventional-pre-commit/releases/tag/v4.1.0
• https://pypi.org/project/conventional-pre-commit/4.1.0/

[bagowix]

Thanks a lot for the quick review and merge! Appreciate the responsiveness - happy to contribute!