gitweb: support to globally disable a snapshot format

Allow Gitweb administrators to set a 'disabled' key in the
%known_snapshot_formats hash to disable a specific snapshot format.

All formats are enabled by default to maintain backwards compatibility.
Signed-off-by: NMark Rada <marada@uwaterloo.ca>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -160,7 +160,8 @@ BEGIN
 	# 	'suffix' => filename suffix,
 	# 	'format' => --format for git-archive,
 	# 	'compressor' => [compressor command and arguments]
-	# 	                (array reference, optional)}
+	# 	                (array reference, optional)
+	# 	'disabled' => boolean (optional)}
 	#
 	'tgz' => {
 		'display' => 'tar.gz',
@@ -494,7 +495,8 @@ sub filter_snapshot_fmts {
 		exists $known_snapshot_format_aliases{$_} ?
 		       $known_snapshot_format_aliases{$_} : $_} @fmts;
 	@fmts = grep {
-		exists $known_snapshot_formats{$_} } @fmts;
+		exists $known_snapshot_formats{$_} &&
+		!$known_snapshot_formats{$_}{'disabled'}} @fmts;
 }
 
 our $GITWEB_CONFIG = $ENV{'GITWEB_CONFIG'} || "++GITWEB_CONFIG++";
@@ -5166,6 +5168,8 @@ sub git_snapshot {
 		die_error(400, "Unknown snapshot format");
 	} elsif (!grep($_ eq $format, @snapshot_fmts)) {
 		die_error(403, "Unsupported snapshot format");
+	} elsif ($known_snapshot_formats{$format}{'disabled'}) {
+		die_error(403, "Snapshot format not allowed");
 	}
 
 	if (!defined $hash) {