Track reviewed files per diff version

Problem to solve

In merge requests, as I review files, review discussions, and more changes/discussions are added, it's very difficult to keep track of what you have reviewed in the past and what still needs to be reviewed.

Intended users

Developers

Further details

Ultimately we should use this information, so that it is easy to review only the new changes since a person last reviewed a merge request.

Crucible

Proposal

• Clicking on a file diff in the merge request diff should mark it as read for that version immediately
• Clicking on a file name in the merge request file tree should mark it as read for that version after 1000ms, if they haven't clicked to a different file already. This is to accommodate miss-clicks in the file tree causing the file to be marked as read incorrectly. The debounce should be short enough that there is enough time to review a tiny change, but long enough to allow someone to realize they clicked on the wrong file
• The file tree should show unread files in bold
• There should be a button to mark all files read
• There should be a button to mark all files unread

Links / references

https://confluence.atlassian.com/crucible/using-progress-tracking-298977446.html