Resume code review after source branch changes
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## Problem to solve
While performing a code review, if the source branch changes and I reload the page, my in progress review may have comments against lines that were added and now removed, and I can no longer access them.
## Further details
This is a hard problem to solve because it creates a situation where the user needs to jump backwards and forwards between revisions.
## Proposal
I should be able to jump to old versions of a file to see my draft comments on them.
## Links / references
issue