Compare merge request versions smarter

Description

Today we compare MR versions by simply diff the head of version1 and version2. This is problematic when a MR gets rebased with the target branch. Instead of seeing the relevant changes, it is polluted with unrelated target branch changes.

side note: It is unrealistic for an organization to prevent rebasing MR's. This is a common practice to fix CI pipelines, squash fixups, get latest code from related merged MR's.

Proposal

Instead of simply comparing version1 with version2, we compare version1 difference from target with version2 difference from target. This way we only see relevant changes which matches the user's expectations.

This is commonly done on the CLI using a command like:

diff <(git diff master...version1) <(git diff master...version2)