gitweb: feed generator metadata

Add <generator> tag to RSS and Atom feed. Versioning info (gitweb/git
core versions, separated by a literal slash) is stored in the
appropriate attribute for the Atom feed, and in the tag content for the
RSS feed.

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -6085,6 +6085,7 @@ XML
 			      "<link>$alt_url</link>\n" .
 			      "</image>\n";
 		}
+		print "<generator>gitweb v.$version/$git_version</generator>\n";
 	} elsif ($format eq 'atom') {
 		print <<XML;
 <feed xmlns="http://www.w3.org/2005/Atom">
@@ -6111,6 +6112,7 @@ XML
 		} else {
 			print "<updated>$latest_date{'iso-8601'}</updated>\n";
 		}
+		print "<generator version='$version/$git_version'>gitweb</generator>\n";
 	}
 
 	# contents