D7867: rust-hg-path: add useful methods to `HgPath`

[Alphare (Raphaël Gomès)]

Alphare added inline comments.

INLINE COMMENTS

> kevincox wrote in hg_path.rs:169
> I don't think we should have this method. It provides us no way to ensure that the invariants of this type are upheld. It is slightly more typing but I think we should recommend converting to a slice, doing the mutation, then converting back to `HgPath` then we can at least to validation (possibly only in debug builds) in the constructor.

Fair enough.

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D7867/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D7867

To: Alphare, #hg-reviewers, kevincox
Cc: durin42, kevincox, mercurial-devel