[llvm-dev] [Openmp-dev] [Github] RFC: linear history vs merge commits (original) (raw)

David Greene via llvm-dev llvm-dev at lists.llvm.org
Tue Jan 29 14:48:14 PST 2019

Tom Stellard via Openmp-dev <openmp-dev at lists.llvm.org> writes:

As part of the migration of LLVM's source code to github, we need to update our developer policy with instructions about how to interact with the new git repository. There are a lot of different topics we will need to discuss, but I would like to start by initiating a discussion about our merge commit policy. Should we:

1. Disallow merge commits and enforce a linear history by requiring a rebase before push. 2. Allow merge commits. 3. Require merge commits and disallow rebase before push. I'm going to propose that if we cannot reach a consensus that we adopt policy #1, because this is essentially what we have now with SVN.

I agree with proposing #1 in general. It results in a nice clean history and will be familiar to everyone working on the project.

However, there is a place for merge commits. If there's a bug in a release and we want to make a point release, it might make sense to make a commit on the release branch and then merge the release branch to master in order to ensure the fix lands there as well. Another option is to commit to master first and then cherry-pick to release. A third option is to use the "hotfix branch" method of git flow [1], which would result in a merge commit to the release branch and another merge commit to master.

I've seen projects that commit to release first and then merge release to master and also projects that commit to master and cherry-pick to release. I personally haven't seen projects employ the git flow hotfix branch method rigorously.

But GitHub is read-only for almost a year, right? So we really don't have to decide this for a while. I have not tried using the monorepo and committing to SVN with it. How does that work? What would it do with merge commits?

                          -David

[1] https://nvie.com/posts/a-successful-git-branching-model

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