gitweb: Add navigation to select side-by-side diff

Add to the lower part of navigation bar (the action specific part)
links allowing to switch between 'inline' (ordinary) diff and
'side by side' style diff.

It is not shown for combined / compact combined diff.

Signed-off-by: Kato Kazuyoshi <[email protected]>
Signed-off-by: Jakub Narebski <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: kzys

gitweb/gitweb.perl

@@ -7164,6 +7164,7 @@ sub git_blobdiff {
 		my $formats_nav =
 			$cgi->a({-href => href(action=>"blobdiff_plain", -replay=>1)},
 			        "raw");
+		$formats_nav .= diff_style_nav($diff_style);
 		git_header_html(undef, $expires);
 		if (defined $hash_base && (my %co = parse_commit($hash_base))) {
 			git_print_page_nav('','', $hash_base,$co{'tree'},$hash_base, $formats_nav);
@@ -7221,6 +7222,27 @@ sub git_blobdiff_plain {
 	git_blobdiff('plain');
 }
 
+# assumes that it is added as later part of already existing navigation,
+# so it returns "| foo | bar" rather than just "foo | bar"
+sub diff_style_nav {
+	my ($diff_style, $is_combined) = @_;
+	$diff_style ||= 'inline';
+
+	return "" if ($is_combined);
+
+	my @styles = (inline => 'inline', 'sidebyside' => 'side by side');
+	my %styles = @styles;
+	@styles =
+		@styles[ map { $_ * 2 } 0..$#styles/2 ];
+
+	return join '',
+		map { " | ".$_ }
+		map {
+			$_ eq $diff_style ? $styles{$_} :
+			$cgi->a({-href => href(-replay=>1, diff_style => $_)}, $styles{$_})
+		} @styles;
+}
+
 sub git_commitdiff {
 	my %params = @_;
 	my $format = $params{-format} || 'html';
@@ -7250,6 +7272,7 @@ sub git_commitdiff {
 				$cgi->a({-href => href(action=>"patch", -replay=>1)},
 					"patch");
 		}
+		$formats_nav .= diff_style_nav($diff_style, @{$co{'parents'}} > 1);
 
 		if (defined $hash_parent &&
 		    $hash_parent ne '-c' && $hash_parent ne '--cc') {