Deal with a force-pushed PR branch

[roblourens]

• A PR branch is force-pushed
• PR extension notifies me that the PR has updates
• I click "pull"
• Now I have to merge changes between the two versions of the branch

Currently I have to go to the command line myself to reset the branch to the upstream version which is annoying, because this is a common PR workflow. I think the typical way to do this is to fetch, then git reset --hard upstream/branch.

There should somehow be an option to reset my branch to the upstream branch. If the local commits are my own commits, we wouldn't want to lose those, so maybe there should be a separate button, or the extension can notify me after I click "pull" and ask me whether to merge or reset. Either way there should be some SCARY TEXT so I know that commits will be lost...