git: For conflicted files, set project diff excerpts using conflicts only (#44263)

It's just distracting having excerpts for all the successfully merged
hunks.

Release Notes:

- git: The project diff now focuses on merge conflicts for files that
have them.
66c7bdf037Cole Miller committed on 12/6/2025, 2:20:14 AM· committed by GitHubparent363fbbf
1 file changedLine totals unavailable