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)
```
issue