rhg: more efficient `HgPath::join`...
rhg: more efficient `HgPath::join`
This commit makes `HgPath::join` slightly more efficient
by avoiding one copy.
It also avoids a particularly inefficient (quadratic) use of
`HgPath::join` by using a new mutating function `HgPathBuf::push` instead.
The name for `HgPathBuf::push` is chosen by analogy to `PathBuf::push`.
Differential Revision:
https://phab.mercurial-scm.org/D11721