Merge pull-requests by commit disabled?

[v4hn]

I just wanted to merge #278 and found the Create a merge commit field disabled:

Create a merge commit
All commits from this branch will be added to the base branch via a merge commit.
Not enabled for this repository

@davetcoleman @mlautman @rhaschke Did someone disable this option?
I guess it is still possible to do this by hand in git, right?
It's not a big deal for this request, but in general I would prefer to have this possibility.

[davetcoleman]

I don't remember exactly, but this was probably me. Why do we want this enabled, though? We never use that functionality as it makes a sloppy git history. Our policy is:

Squash-Merge If Possible
Pull-requests with a single commit should always be squash-merged (github supports this via a drop-down list on the “merge” button). If a request contains “fixup commits” it should also be squash-merged. If you are unsure this is to the requestor’s liking, ask them.

[rhaschke]

The citation primarily refers to single commits and fixup commits, which indeed should not clutter the git history. Merge-commits make a lot of sense if there are multiple, clearly distinguishable commits in a single PR!

[davetcoleman]

For clearly distinguishable commits in a single PR we've all agreed we want rebase merging:

[rhaschke]

Often that's a viable option, yes. However, rebase-merging also disguises the extension of a merge (you don't see the start and end of the related commits anymore) and the PR id is not reported by github.
For this reason, I prefer merge commits in other projects, although I try not to merge branches that were branched off very deep in the past. In this case, I first rebase and then merge-commit.

[v4hn]

For clearly distinguishable commits in a single PR we've all agreed we want rebase merging:

I'm not aware of an agreement to never use merge commits in moveit and neither Robert nor I seem to agree.

• single commits - > squash
• multiple fixup-style commits - > squash
• multiple independent commits -> rebase and merge
• multiple clean commits with common ground and some relation - > merge commit.

one of git's design goals are short-living feature branches that can be merged.
So I really don't think it makes sense to disable merges...

[davetcoleman]

Sounds good, I've re-enabled merging. Can you copy that policy your wrote out on our Pull Request page please? You can just edit on Github:
https://github.com/ros-planning/moveit.ros.org/blob/gh-pages/documentation/contributing/pullrequests/index.markdown