Make merge-ref diffs the default comparison mode
Problem to solve
Merge request diffs are currently calculated by
git diff target...source which compares
target with the merge base of
source. This works well until changes from the target branch are merged in to the source branch, creating a complete mess of the diff.
In previous iterations we've added a new diff mode, and implemented commenting support. This issue will make it the default comparison mode.
This should definitely be feature flagged, so that it can be enabled for individual projects and groups for testing.
When viewing a merge request diff, when comparing between Latest version and master this should default to comparing using the
merge-ref. The merge-base method should not be available any more.