hooks: add url to changegroup, incoming, prechangegroup, pretxnchangegroup hooks
all repository classes now have url() method that returns url of repo.
#!/bin/shhg init aecho a > a/ahg --cwd a ci -A -m ahg clone a becho b > b/bhg --cwd b ci -A -m bchmod 100 a/.hghg --cwd b push ../achmod 700 a/.hg