$ hg init a

  $ echo a > a/a

  $ hg -R a ci -A -m a

  adding a

  $ hg clone a b

  updating to branch default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo b > b/b

  $ hg -R b ci -A -m b

  adding b

  $ chmod 100 a/.hg/store

  $ hg -R b push a

  pushing to a

  abort: could not lock repository a: Permission denied

  $ chmod 700 a/.hg/store