tests/blacklists/nix

typing: add trivial type hints to `mercurial.scmutil`

There's still a lot to go, but there's a lot here already, so I tried to keep it
to obvious/trivial things.  I didn't bother with contexts, matchers, and
revisions that can be `bytes | int | None`.

# Tests to be disabled when building and testing in the Nix sandbox.

# tests enforcing "/usr/bin/env" shebangs, which are patched for nix
test-run-tests.t
test-check-shbang.t

# doesn't like the extra setlocale warnings emitted by the nix bash wrappers
test-locale.t