dirstate-cext: properly invalidate mtime and data in `set_untracked`
This was forgotten about in the initial implementation and was revealed while
adding the `dirstate-v2` variant of `test-issue660.t`. Neither the existing
Python implementation nor the upcoming Rust implementation suffer from this
bug since they respectively have `None` and `Option<T>` to represent the lack
of information.
Differential Revision: https://phab.mercurial-scm.org/D12414
#require cargo test-repo
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "$TESTDIR"/../rust
Check if Cargo.lock is up-to-date. Will fail with a 101 error code if not.
$ cargo check --locked --all --quiet
However most CIs will run `cargo build` or similar before running the tests, so we need to check if it was modified
$ testrepohg diff Cargo.lock