gitweb: accept trailing "/" in $project_list

The current code is removing the trailing "/", but computing the string
length on the previous value, i.e. with the trailing "/". Later in the
code, we do

  my $path = substr($File::Find::name, $pfxlen + 1);

And the "$pfxlen + 1" is supposed to mean "the length of the prefix, plus
1 for the / separating the prefix and the path", but with an incorrect
$pfxlen, this basically eats the first character of the path, and yields
"404 - No projects found".

While we're there, also fix $pfxdepth to use $dir, although a change of 1
in the depth shouldn't really matter.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -2661,8 +2661,8 @@ sub git_get_projects_list {
 		my $dir = $projects_list;
 		# remove the trailing "/"
 		$dir =~ s!/+$!!;
-		my $pfxlen = length("$projects_list");
-		my $pfxdepth = ($projects_list =~ tr!/!!);
+		my $pfxlen = length("$dir");
+		my $pfxdepth = ($dir =~ tr!/!!);
 		# when filtering, search only given subdirectory
 		if ($filter) {
 			$dir .= "/$filter";