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
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "1000000 0"
touch b
hg add b
rm b
hg commit -A -m"comment #1" -d "1000000 0"