Process change suggestion: squash-and-merge PRs

[chalin]

Followup to #540 (comment).

@LisaFC - I'd like to suggest a process change: squash-and-merge PRs from now on rather than doing a default merge. This will keep the repo history clean, and make it more obvious which changes any given PR is introducing. It will also be helpful to PR authors as it usually forces PR authors, who might be working from a very old version of the repo, to rebase and resolve any merge conflicts (using their expertise of the code changes they're introducing) before their PR can be accepted for merging.

Thoughts?

/cc @nate-double-u @celestehorgan

[chalin]

Related:

• new branch protection rule: must pass CLA check, must be up-to-date #722

[emckean]

I like the idea of moving to squash-and-merge for PRs. It looks like if we remove the "allow merge commits" setting then this will become the default (but admins can still merge-commit): (see dotnet/runtime#260). @chalin is that your understanding of the settings work?

[chalin]

@emckean - right: ensuring that "allow merge commits" is unchecked and that "allow squash merging" is checked seems to be the way to go.

[chalin]

@emckean or @LisaFC: have you changed the settings? If so, note that the choice of merge is a "sticky", so on your next PR merge you'll need to manually select to squash the PR. For subsequent PRs, the setting will be squash.

[chalin]

@LisaFC: any issue in implementing this?