gitweb: change call pattern for git_commitdiff

Since we are going to introduce an additional parameter for
git_commitdiff to tune patch view, we switch to named/hash-based
parameter passing for clarity and robustness.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 9a11be3..63e93a2 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -5411,7 +5411,8 @@
 }
 
 sub git_commitdiff {
-	my $format = shift || 'html';
+	my %params = @_;
+	my $format = $params{-format} || 'html';
 
 	my $patch_max;
 	if ($format eq 'patch') {
@@ -5619,12 +5620,12 @@
 }
 
 sub git_commitdiff_plain {
-	git_commitdiff('plain');
+	git_commitdiff(-format => 'plain');
 }
 
 # format-patch-style patches
 sub git_patch {
-	git_commitdiff('patch');
+	git_commitdiff(-format => 'patch');
 }
 
 sub git_history {