rust-filepatterns: match exact `rootglob`s with a `HashSet`, not in the regex...
rust-filepatterns: match exact `rootglob`s with a `HashSet`, not in the regex
This optimization yields some very interesting results in `rootglob`-heavy
repositories.
I build a test repository of the following structure:
```
root
/<uuid>/build/empty_file
... repeat for 4000 entries
```
and a `.hgignore` containing the corresponding 4000 `rootglob` entries pointing
to all `build/` folders.
Rust+c `hg status` goes from 350ms down to 110ms.
Differential Revision:
https://phab.mercurial-scm.org/D8491
