When merging an MR, the squash checkbox isn't always supported
Summary
Follow-up to https://gitlab.com/gitlab-org/gitlab-ce/issues/48130#note_105760464
Sometimes, when I click the "Squash" checkbox in the MR widget then press "Merge", a squash is not performed before the MR is merged.
Steps to reproduce
???
Example Project
Seen when merging gitlab-pages!94 (merged) . I clicked the "squash" checkbox and hit merge immediately after, from memory. Although maybe there was an MWPS involved.
Now look at master :( : https://gitlab.com/gitlab-org/gitlab-pages/commits/master
What is the current bug behavior?
The MR is not squashed, despite "squash" being requested
What is the expected correct behavior?
The MR should have been squashed. Now master looks disgusting and there's no way to clean it up.
Relevant logs and/or screenshots
Output of checks
This bug happens on GitLab.com
Possible fixes
I'm not sure what's going on here. What does clicking the "squash" checkbox do? Any fancy JS in the background? Could that be racing with the fancy JS that happens when we press the "merge" button?
Since this bad merge happened literally today, perhaps someone can find the HTTP logs for this specific incident?
It's tempting to blame this on the Vue refactor of the MR page, but I don't have any evidence for it ;)