rhg: read [paths] for --repository value
hg parses -R and --repository CLI arguments "early" in order to know which
local repository to load config from. (Config can then affect whether or how to
The value of of those arguments can be not only a filesystem path, but also an
alias configured in the [paths] section. This part was missing in rhg and
this patch implements that.
The current patch still lacks functionality to read config of current repository
if we are not at root of repo. That will be fixed in upcoming patches.
A new crate home is added to get path of home directory.
Differential Revision: https://phab.mercurial-scm.org/D10296