Bug 297684 – [EWS] checkout-pull-request step failed with an error stating that the branch already exists, worked on retry

• Component: Tools / Tests
• Status: RESOLVED DUPLICATE

[Ryan Haddad]

In https://ews-build.webkit.org/#/builders/121/builds/44570, the checkout-pull-request step failed with the following:
```
git remote set-url kmiller68 https://github.com/kmiller68/WebKit.git

git fetch kmiller68 eng/Workers-should-handle-btoa-OOM-gracefully
From https://github.com/kmiller68/WebKit
 * branch                      eng/Workers-should-handle-btoa-OOM-gracefully -> FETCH_HEAD
 * [new branch]                eng/Workers-should-handle-btoa-OOM-gracefully -> kmiller68/eng/Workers-should-handle-btoa-OOM-gracefully

git checkout -b eng/Workers-should-handle-btoa-OOM-gracefully
fatal: a branch named 'eng/Workers-should-handle-btoa-OOM-gracefully' already exists
```

The build worked on a retry, so we should make our steps more resilient to this kind of error.

[Radar WebKit Bug Importer]

<rdar://problem/158797929>

[Aakash Jain]

the previous step `clean-up-git-repo` failed to delete that branch for some reason, see logs:

error: Cannot delete branch 'eng/Workers-should-handle-btoa-OOM-gracefully' checked out at ...
error: branch '*' not found.

https://ews-build.webkit.org/#/builders/121/builds/44570/steps/4/logs/stdio

[Sam Sneddon [:gsnedders]]

We have:

```
git checkout origin/main -f
 in dir /Volumes/Data/worker/visionOS-2-Simulator-Build-EWS/build (timeout 300 secs)
 watching logfiles {}
 argv: [b'git', b'checkout', b'origin/main', b'-f']
 using PTY: False
error: pathspec 'origin/main' did not match any file(s) known to git
```

This is slightly strange (it also shows the ambiguity problem of `git-checkout` given it's complaining about paths!) — but it implies we either have no `origin` or the `origin` has no `main` branch.

Looking at the worker:

```
buildbot@ews221 ~ % git -C /Volumes/Data/worker/visionOS-2-Simulator-Build-EWS/build remote -v  
elijahsawyers	https://github.com/elijahsawyers/WebKit.git (fetch)
elijahsawyers	https://github.com/elijahsawyers/WebKit.git (push)
origin	https://github.com/WebKit/WebKit.git (fetch)
origin	PUSH_DISABLED_BY_ADMIN (push)
buildbot@ews221 ~ % git -C /Volumes/Data/worker/visionOS-2-Simulator-Build-EWS/build for-each-ref refs/heads refs/remotes
934f88404e9fa471e2254c6ddaef34af3fafe7a4 commit	refs/heads/eng/REGRESSION-269745-main-Inserting-a-PathSeg-with-NaN-coordinates-into-a-path-element-can-result-in-NaN-StrokeBoundingBox
9490d860bc447da9a01f2505d49fec7a85d2db88 commit	refs/heads/eng/esawyers/297338
934f88404e9fa471e2254c6ddaef34af3fafe7a4 commit	refs/heads/main
e2b825f6b6f7810ea1a61c80b599984dacf067b0 commit	refs/remotes/elijahsawyers/eng/esawyers/297338
```

So we have the remote configured — but we've either never fetched from it or we've deleted the branches we fetched from it. We don't seem to have logs far enough back to figure out how it got in this state, but it's been in this state for a while.

And then, as Aakash mentioned before, because we don't have a detached HEAD:

```
/bin/bash --posix -o pipefail -c 'git branch | grep -v '"'"' main$'"'"' | grep -v '"'"'HEAD detached at'"'"' | xargs git branch -D || true'
 in dir /Volumes/Data/worker/visionOS-2-Simulator-Build-EWS/build (timeout 300 secs)
 watching logfiles {}
 argv: [b'/bin/bash', b'--posix', b'-o', b'pipefail', b'-c', b"git branch | grep -v ' main$' | grep -v 'HEAD detached at' | xargs git branch -D || true"]
 using PTY: False
error: branch '*' not found.
error: Cannot delete branch 'eng/Workers-should-handle-btoa-OOM-gracefully' checked out at '/Volumes/Data/worker/visionOS-2-Simulator-Build-EWS/build'
Deleted branch eng/Avoid-GNU-folding-constant-warnings (was 49119822a1c1).
```

Some of the problem here is we're ending up with `*` because we're trying to parse the output of `git-branch` (a "porcelain" command). I expect what we want to do is something more like:

```
git for-each-ref --format='delete %(refname) %(objectname)' refs/heads | grep -v '^delete refs/heads/main ' | git-update-ref --stdin
```

(I'm also not entirely sure why exactly we're keeping any of our local branches?)

But because we fail to move to a detached HEAD, we fail to delete the branch, and thus we can't create a new branch with the same name — so this only happens with the same PR in direct succession.

[Aakash Jain]

Fixed in https://commits.webkit.org/306516@main

*** This bug has been marked as a duplicate of bug 306636 ***