"Changes between" (revisions) view after rebase is useless

Summary

After a rebase onto develop, the "Changes between" (revisions diff) becomes cluttered with changes from develop are shown as well as changes related to the MR itself.

Steps to reproduce

create a branch, commit some changes, push, rebase on master, commit some more changes, look on the "changes between" view.

Example Project

See actual changes done on the MR: rbiron/rebase_changes_diff!1 (diffs)

VS what we see from the "see revisions", i.e. if I want to see the 2nd commit (e.g. changes after feedback cycle): https://gitlab.com/rbiron/rebase_changes_diff/merge_requests/1/diffs?diff_id=32208780&start_sha=68297e650697b071cf01bdce4e17ea57de0e5737

What is the current bug behavior?

Changes from the rebase appear in the "changes between" view.

What is the expected correct behavior?

Changes that are included in the "merge to" branch should not appear in the "changes between" view (or at least a toggle)

Relevant logs and/or screenshots

NA - see gitlab repo above.

Output of checks

(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:env:info)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)