Preserve original commit message when auto-merging

[joshk0]

We use automerging functionality in our projects, but the resulting commit messages look like this:

commit 26e79dd35e34deadbeef772aa256b4006f141eff (origin/master, origin/HEAD, master)
Author: Cool Committer <[email protected]>
Date:   Fri Nov 15 21:38:44 2019 -0800

    JIRA-1813, Grant the Foo Team access to Bar (#2857)
    
    [Atlantis] Automatically merging after successful apply

Ideally, the commit message should include as much of the PR OP as possible (e.g. whatever would automatically get populated in the editor when you hit 'Squash and merge'.) I'm definitely in favor of having Atlantis annotate it with a heads up that it was automerged by atlantis, but we like our commit messages a lot as they provide value in a way that is redundant to relying on looking at old GitHub PRs.

Is there a technical reason why this is the case? If not, I'd be happy to take a stab at fixing this.

[lkysow]

No technical reason I can think of off the top of my head. Only thing might be that you need to make an additional API call but shouldn't be too bad.

[pratikmallya]

The extra api call could be avoided if google/go-github#1448 is fixed.

[lkysow]

The extra api call could be avoided if google/go-github#1448 is fixed.

Looks like that just got merged! So I think we just need to update to the latest go-github and then set https://github.com/runatlantis/atlantis/blob/master/server/events/vcs/github_client.go#L225 to ""