When viewing branches in an enlargened window, we now colour the commit shas based on
whether the branch has been merged to a main branch and whether it's been pushed to
the upstream.
This isn't using the exact same code as we use for commits, so it's possible we'll get
a colour mismatch when the user checks out a branch and views the commits in the commits
view, but if we come across that situation we'll just need to fix it.