PR merge branch disappears after closing PR and does not return when reopening

[akomakom]

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Bug

Body

This seems to be new behavior that is impacting CI (Azure Pipelines in my case).

What Works

Creating a new PR creates a merge branch, eg:

$ git ls-remote | grep 1243
From https://github.com/quartz-scheduler/quartz
035a29271a6decb143144a7fa7e75bb5ff424ab2	refs/pull/1243/head
18e5e0e9fae5629e0b7378d567e94af0628c4b60	refs/pull/1243/merge

refs/pull/1243/merge is the branch checked out by CI for PR checks. CI works fine.

What Does Not Work

When I close and then reopen a PR, the merge branch goes away and is not re-created (this is new behavior), eg:

$ git ls-remote | grep 1242
From https://github.com/quartz-scheduler/quartz
51dfbc7aa4d79a8975f42d7cda342b11289b75e0	refs/pull/1242/head

CI runs:

git --force --tags --prune --prune-tags --progress --no-recurse-submodules origin   +refs/heads/*:refs/remotes/origin/* +refs/pull/1242/merge:refs/remotes/pull/1242/merge
fatal: couldn't find remote ref refs/pull/1242/merge

Notes:

• I am not referring to reopening merged PRs, only to closing and reopening an unmerged PR.
• Re-opening is often needed to get checks to run, specifically after yesterday's github outage where checks on PRs from forks were not triggering

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[akomakom]

Thanks @thomassiard

Pushing extra commits to PR branch does indeed work around the issue (except that every contributor needs to be asked to do that on their PRs).

The other options also have their downsides, as you pointed out. Thanks for listing them.

[akomakom]

This may be resolved - today I was able to close/reopen a PR and the merge branch was present.

[krassowski]

This is still happening. Can you reopen this discussion?

[krassowski]

We see this behaviour regularly in jupyter-server/jupyter_releaser#593

[alexander-komarov-ibm]

@krassowski you may need to start a new one, I don't appear to be able to re-open this one.

[nikolaykasyanov]

It actually may have gotten worse, we have PRs that, minutes after reopening, still have no refs/pull/.../merge.

[Davo00]

Do you happen to have any updates on this? I see the issue recurring consistently.