Sometimes you can get stuck in a loop where git stash pop preserves the
stash commit. Dropping that commit if it's a STASH commit after an
update is totally fine.
Add warning before make-update and make-push to alert developers that
running the commands might be destructive. Allow cancelling the command
up to 3 seconds before continuing. Also explain that merge conflicts
warrant a re-run of the command.
Rather than potentially leaving the developer in a state where `git
stash pop` wasn't run, ignore failures in git subtree and let the
developer fix issues and re-run the command. This makes `make-update`
more idempotent.