fix: was_squash_via_merge_commit logic

[joseph-sentry]

Check if the merge commit sha is equal to the sha of the head of the PR because in that case we should also move the commits on the PR to the base branch of the PR.

[codecov-notifications]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.18%. Comparing base (b911b8c) to head (6b1d1ef).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #388      +/-   ##
==========================================
- Coverage   94.18%   94.18%   -0.01%     
==========================================
  Files        1255     1255              
  Lines       46308    46311       +3     
  Branches     1455     1455              
==========================================
+ Hits        43615    43617       +2     
- Misses       2388     2389       +1     
  Partials      305      305              

Flag	Coverage Δ
workerintegration	61.44% <33.33%> (-0.01%)	⬇️
workerunit	90.77% <100.00%> (-0.01%)	⬇️

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[codspeed-hq]

CodSpeed Performance Report

Merging #388 will not alter performance

_{Comparing joey/fix (904eb50) with main (5a06654)¹}

Summary

✅ 9 untouched benchmarks

Footnotes

1. No successful run was found on main (ce3f410) during the generation of this report, so 5a06654 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[michelletran-codecov]

Check if the merge commit sha is equal to the sha of the head of the PR because in that case we should also move the commits on the PR to the base branch of the PR.

What's the context for this change? The rebased changes will have a different SHA, so moving these commits to the base branch will cause a mismatch with commit SHA and the actual commit on the main branch.

[michelletran-codecov]

nit: can you also annotate the types of this function?

[joseph-sentry]

What's the context for this change? The rebased changes will have a different SHA, so moving these commits to the base branch will cause a mismatch with commit SHA and the actual commit on the main branch.

There's a case where the experiment was failing because the head sha and merge commit sha were equivalent. The previous logic in the experiment would count that as a squash, because it was only checking the # of parents, but the previous logic was correctly detecting that as not a squash merge.

[michelletran-codecov]

Seems low risk given the feature flag. 👍