subrepo: use hg.repository instead of creating localrepo directly
this way, extensions' reposetup will be called, which allows for git
subrepos to be handled by hg-git (and I believe the same goes for
svn and hgsubversion)
#!/bin/sh
# test dirstate._dirs refcounting
hg init t
cd t
mkdir -p a/b/c/d
touch a/b/c/d/x
touch a/b/c/d/y
touch a/b/c/d/z
hg ci -Am m
hg mv a z