Feature: Restart rebase automatically when it fails on git-update

Previously we made the user attempt to start the rebase themselves, for some
users this is daunting, and we want `git-update` to be as automatic as possible.

From now on, if the rebase fails for any reason, it is aborted and then
restarted automatically.  This will still require user intervention, but it's at
least one less step.

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Branch:        feature/improve-unsuccessful-rebase-handling-in-git-update
Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>
Merge branch 'feature/improve-unsuccessful-rebase-handling-in-git-update-closes-20'