fish_git_prompt may run certain git commands which may invoke certain
external programs as specified `.git/config`. Prevent this by suppressing
certain git config options.
Fixes#7926.
Also switches the default status order for non-informative to the informative one:
stagedstate invalidstate dirtystate untrackedfiles stashstate
instead of
dirty staged stash untracked
Apparently the grep on FreeBSD doesn't do \s or \t. Since we're
looking for an actual tab, just give it an actual tab.
See https://builds.sr.ht/~faho/job/448496.
Prior to this change, the checks/git.fish test would fail if run from a
git interactive rebase (such as via `git rebase -i --exec 'ninja test'`),
because git itself would inject stuff into the environment. Teach the git
test how to clean up its environment first before running.
This makes the fish_git_prompt variable handlers kick in, meaning we
see the informative chars.
The big question here is what happens if there's a non-UTF-8 locale in
the test.
Theoretically we set LC_CTYPE, but.....
