Automatically update merge request commits tab when new commits are pushed
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## Problem to solve
When I am viewing a merge request and new commits are pushed, I can see a new push event appear in the discussions tab, but the Commits tab doesn't update.
## Proposal
When a new push event occurs, update the commits tab to show all the new commits.
An edge case to consider is if a force push occurs, causing the entire commit list to be replaced. This is fine, but it could mean the diff view becomes out of sync with the commit list if either was previously opened.
## Links / references
issue