Looks like we broke the `hasLocalChanges` check in the git client
when we moved it over from the merge script. The problem is that
we are using `git` in the first argument of `git.run`. That
means that we under-the-hood run `git git <..>`.
This commit fixes that, but also switches to a better variant
for ensuring no local changes because it exits with non-zero
when there are local changes.
PR Close#37489
a3313709ea