The commit range in the UI follows a half-open, half-closed convention:
(,]. When reviewing a range of commits, the beforeCommitID should be set
to the commit immediately preceding the first selected commit. For
single-commit reviews, we must identify and use the previous commit of
that specific commit.
The endpoint ViewPullFilesStartingFromCommit is currently unused and can
be safely removed.
Fix#35157
Replace #35184
Partially extract from #35077
be2a6b4414