Checking how hg behaves when one side of a pull/push doesn't support

some capability (because it's running an older hg version, usually).

  $ hg init repo1

  $ cd repo1

  $ echo a > a; hg add -q a; hg commit -q -m a

  $ hg bookmark a

  $ hg clone -q . ../repo2

  $ cd ../repo2

  $ touch $TESTTMP/disable-lookup.py

  $ disable_cap() {

  >   rm -f $TESTTMP/disable-lookup.pyc # pyc caching is buggy

  >   cat <<EOF > $TESTTMP/disable-lookup.py

  > from mercurial import extensions, wireprotov1server

  > def wcapabilities(orig, *args, **kwargs):

  >   cap = orig(*args, **kwargs)

  >   cap.remove(b'$1')

  >   return cap

  > extensions.wrapfunction(wireprotov1server, '_capabilities', wcapabilities)

  > EOF

  > }

  $ cat >> ../repo1/.hg/hgrc <<EOF

  > [extensions]

  > disable-lookup = $TESTTMP/disable-lookup.py

  > EOF

  $ hg pull ssh://user@dummy/repo1 -r tip -B a

  pulling from ssh://user@dummy/repo1

  no changes found

  $ disable_cap lookup

  $ hg pull ssh://user@dummy/repo1 -r tip -B a

  pulling from ssh://user@dummy/repo1

  abort: other repository doesn't support revision lookup, so a rev cannot be specified.

  [255]

  $ disable_cap pushkey

  $ hg pull ssh://user@dummy/repo1 -r tip -B a

  pulling from ssh://user@dummy/repo1

  abort: remote bookmark a not found!

  [10]