skip loading a diff when we just need the conflicts from it

[ajtmccarty]

should help performance when merging a branch b/c it allows us to skip loading the whole diff to check if there are any conflicts. for a small diff, this does not really matter, but for a huge diff, skipping loading the whole diff makes a big difference

[codspeed-hq]

CodSpeed Performance Report

Merging #5529 will not alter performance

_{Comparing ajtm-01202025-skip-loading-diff-for-conflicts (3f2d75c) with stable (5bf43e2)}

Summary

✅ 10 untouched benchmarks

[ogenstad]

What does this mean with regards to providing a diff object for the actual merge? I.e. after a branch has been merged we will want to look at some sort of diff object in order to figure out what events we need to generate.

[ajtmccarty]

What does this mean with regards to providing a diff object for the actual merge? I.e. after a branch has been merged we will want to look at some sort of diff object in order to figure out what events we need to generate.

the method where the actual merge logic happens is DiffMerge.merge_graph, which is called after this conflicts check. merge_graph gets the latest version of the diff from the database before running the actual merge queries, so that will continue working as expected