Proposal: Label and message for PRs with Merge Commits

[Waterdrips]

If there's a merge commit pushed to a PR can we add a label and post a message to the PR from Derek saying that Merge Commits are not allowed, and provide info on how to remove it, and rebase.

Can we detect easily merge commits? Is it the format of the commit message or are they different?

Expected Behaviour

A PR with a merge commit pushed to it should get a label from derek and a message posted about why and how to fix it.
2 scenarios

1. A PR is raised and there is already a merge commit
2. A Merge Commit is pushed to the PR

Should this be optional? Configured in the yaml? What about for repos that dont have the config set? Do we enable or disable by default?

Current Behaviour

No feature

Possible Solution

Add a check into Derek that fulfils the 2x scenarios if enabled.

[alexellis]

Thanks for the suggestion, this seems like it could be automated and save us some time explaining the same thing over and over. Are you wanting to work on this @Waterdrips?

[Waterdrips]

I am interested in doing this, but I have quite a lot of WIP so I'd rather not pick it up and block someone else from doing this if they wanted.

When I have my WIP down to a more manageable level I'll come back and see if this is still unassigned and take it on.