patch.py: re-add the ability to use an external patch program This is now invoked by default only if ui.patch is set. Otherwise, we use our built-in patch. If that fails because it can't find any valid hunks, we'll fall back to trying the external patch command.

#!/bin/sh

hg init a
cd a
hg init b
echo x > b/x
echo '# should print nothing'
hg st
echo '# should print ? b/x'
hg st b/x

hg add b/x

echo '# should print A b/x'
hg st
echo '# should forget b/x'
hg revert --all
echo '# should print nothing'
hg st b