Re: grep open pull requests

From: Jeff King <peff@peff.net>
Date: Jan 19, 2017, 19:02 UTC
Message-ID: <20170119190227.opjisryyqn766tqy@sigill.intra.peff.net>
In-Reply-To: <276f6ed9-ff06-a00f-b88a-4d40d55c6d40@nottheoilrig.com>

On Thu, Jan 19, 2017 at 11:12:03AM -0700, Jack Bates wrote:

Show 6 quoted lines

> I have a couple questions around grepping among open pull requests.
> 
> First, "git for-each-ref --no-merged": When I run the following,
> it lists refs/pull/1112/head, even though #1112 was merged in commit
> ced4da1. I guess this is because the tip of refs/pull/1112/head is 107fc59,
> not ced4da1?

Right. Git's `--no-merged` is about commit ancestry.

Show 5 quoted lines

> This maybe shows my lack of familiarity with Git details,
> but superficially the two commits appear identical -- [1] and [2] --
> same parent, etc. Nonetheless they have different SHA-1s.
> I'm not sure why that is -- I didn't merge the commit --
> but regardless, GitHub somehow still connects ced4da1 with #1112.

The commits differ only in the committer timestamp. Try:

  diff -u <(git cat-file commit 107fc5910) \
          <(git cat-file commit ced4da132)

Is it possible that somebody cherry-pick or rebased it? Looking at the history of apache/trafficserver, I don't see any merges, which implies to me that the project is using a rebase workflow to merge PRs.

It's much trickier to find from the git topology whether a particular history contains rebased versions of commits. You can look at the --cherry options to "git log", which use patch-ids to try to equate commits. Something like:

  git for-each-ref --format='%(refname)' 'refs/pull/*/head' |
  while read refname; do
	if test -z "$(git rev-list --right-only --cherry-pick -1 origin...$refname)
	then
		echo "$refname: not merged"
	fi
  done

That's obviously much less efficient than `--no-merged`, but it should generally work. The exception is if the rebase changed the commit sufficiently that its patch-id may have changed.

> So my question is, how are they doing that,

I suspect the answer is "somebody clicked the rebase button GitHub" which simultaneously did the rebase and marked the PR as merged.

> Lastly, a question more about GitHub than Git, but: Given the way GitHub is
> setup, I hope I can get a list of unmerged pull requests from Git alone. Can
> you think of a way to list *open* pull requests,
> or is that status only available out of band?

That information isn't reflected in the git topology. It's in GitHub's database. You can ask the API:

  https://developer.github.com/v3/

There are libraries to help with that:

  https://developer.github.com/libraries/

I think that's probably the best answer to your "unmerged" question, too. Ask the API which PRs are unmerged, and then do whatever git-level analysis you want based on that.

-Peff