gitweb: Better processing format string in custom links in navbar

Make processing format string in custom links in action bar ('actions'
feature) more robust.  Now there would be no problems if one of
expanded values (for example project name, of project filename)
contains '%'; additionally format string supports '%' escaping by
doubling, i.e. '%%' expands to '%'.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

gitweb/gitweb.perl

@@ -290,10 +290,10 @@ our %feature = (
 
 	# The 'default' value consists of a list of triplets in the form
 	# (label, link, position) where position is the label after which
-	# to inster the link and link is a format string where %n expands
+	# to insert the link and link is a format string where %n expands
 	# to the project name, %f to the project path within the filesystem,
 	# %h to the current hash (h gitweb parameter) and %b to the current
-	# hash base (hb gitweb parameter).
+	# hash base (hb gitweb parameter); %% expands to %.
 
 	# To enable system wide have in $GITWEB_CONFIG e.g.
 	# $feature{'actions'}{'default'} = [('graphiclog',
@@ -2866,14 +2866,19 @@ sub git_print_page_nav {
 	$arg{'tree'}{'hash_base'} = $treebase if defined $treebase;
 
 	my @actions = gitweb_check_feature('actions');
+	my %repl = (
+		'%' => '%',
+		'n' => $project,         # project name
+		'f' => $git_dir,         # project path within filesystem
+		'h' => $treehead || '',  # current hash ('h' parameter)
+		'b' => $treebase || '',  # hash base ('hb' parameter)
+	);
 	while (@actions) {
-		my ($label, $link, $pos) = (shift(@actions), shift(@actions), shift(@actions));
+		my ($label, $link, $pos) = splice(@actions,0,3);
+		# insert
 		@navs = map { $_ eq $pos ? ($_, $label) : $_ } @navs;
 		# munch munch
-		$link =~ s#%n#$project#g;
-		$link =~ s#%f#$git_dir#g;
-		$treehead ? $link =~ s#%h#$treehead#g : $link =~ s#%h##g;
-		$treebase ? $link =~ s#%b#$treebase#g : $link =~ s#%b##g;
+		$link =~ s/%([%nfhb])/$repl{$1}/g;
 		$arg{$label}{'_href'} = $link;
 	}