Git-Flow, smarter detection of remote feature finished

When SmartGit detects that main branch is ahead of feature branch, the default git-flow action is to merge or rebase changes. However, if it could be just a tiny bit smarter it could detect that the reason it's ahead is that the feature branch has already been merged into main (typically because of acceptance of pull request), and the default action should now be to Finish the feature, by fast-forward merging to main, checking out main, and deleting the local feature branch (which is probably local-only now, as the remote feature branch will have been deleted as part of the remote closing of that feature)