template: fold template() into __call__, minor optimizations - use non-grouping operator to avoid some extra processing - avoid copying and updating defaults - unnest main template body - avoid returning extra empty string if format

#!/bin/sh

hg init

echo "Is there an error message when trying to diff non-existing files?"
hg diff not found

echo "Is there an error message when trying to add non-existing files?"
hg add not found