Modernize git calling conventions in hook templates

Modernize git calling conventions in hook templates

The hook templates were still using/referencing 'git-foo' instead of
'git foo.'  This patch updates the sample hooks to use the modern
conventions instead.

Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>