Reorder files in diffs in merge requests

Description including problem, use cases, benefits, and/or goals

Code should tell a story. You're building feature X by doing Y.

Many people are of the opinion that code review should follow that story. You want the reviewer to focus on the critical changes and only later look into the 34 files you removed or the rename you followed through in other files.

By being able to reorder the files of a diff in a merge request, you could make it easier to review your code.

This should follow the ability to collapse files in diffs (https://gitlab.com/gitlab-org/gitlab-ce/issues/14103), so we are aware of the UX.

Proposal

Allow for everyone with developer permission or higher to change the order of the diffs in a MR. The change will be for everyone.

I can imagine two UX implementations, but welcome others:

• you drag the entire top bar of a file in the diff (this is preferable)
• we add a little hamburger / drag icon to each file in the diff

Links / references

Should be done after https://gitlab.com/gitlab-org/gitlab-ce/issues/14103

original issue

Sometimes, code review would be much easier for me if I could read the patch in a better order - for example base function definitions being in the beginning of the diff. Could you add a way to change the ordering of the files in the diff to make it more human-readable?