rhg: Use binary search in manifest lookup...
rhg: Use binary search in manifest lookup
… instead of linear scan, when looking for a single entry based on its path.
Manifest entries are sorted by path, but are variable-size so we can’t use
the standard library’s `[T]::binary_search`. We can still jump to a byte
index and then look around for entry boundaries.
Differential Revision:
https://phab.mercurial-scm.org/D11932
