tests/test-pull-permission.t

revsets: let parents() return parents of working dir

This patch makes the 'set' argument to revset function parents() optional.
Like p1() and p2(), if no argument is given, returns the parent(s) of the
working directory.

Morally equivalent to 'p1()+p2()', as expected.

  $ mkdir a
  $ cd a
  $ hg init
  $ echo foo > b
  $ hg add b
  $ hg ci -m "b"

  $ chmod -w .hg/store

  $ cd ..

  $ hg clone a b
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ chmod +w a/.hg/store # let test clean up

  $ cd b
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 1 changesets, 1 total revisions