Support commitmsg configurations without destination

In this case, just don't send any commit messages. This is still useful
for cases where we want a pingurl to be hit as a result of the push.

commitmsg.py

@@ -306,6 +306,12 @@ def parse_annotated_tag(lines):
 		l = sys.stdin.readline()
 		if not l: break
 
+		# If no receiver is defined, just eat up all the input but don't send
+		# any email. We still want to run to completion so that we can send
+		# the pingurls, if any
+		if not c.has_option('commitmsg', 'destination'):
+			continue
+
 		(oldobj, newobj, ref) = l.split()
 
 		# Build the email