gitweb: Allow UTF-8 encoded CGI query parameters and path_info

Gitweb forgot to turn query parameters into UTF-8. This results in a bug
that one cannot search for a string with characters outside US-ASCII.  For
example searching for "Michał Kiedrowicz" (containing letter 'ł' - LATIN
SMALL LETTER L WITH STROKE, with Unicode codepoint U+0142, represented
with 0xc5 0x82 bytes in UTF-8 and percent-encoded as %C5%82) result in the
following incorrect data in search field

	MichaÅ\202 Kiedrowicz

This is caused by CGI by default treating '0xc5 0x82' bytes as two
characters in Perl legacy encoding latin-1 (iso-8859-1), because 's'
query parameter is not processed explicitly as UTF-8 encoded string.

The solution used here follows "Using Unicode in a Perl CGI script"
article on http://www.lemoda.net/cgi/perl-unicode/index.html:

	use CGI;
	use Encode 'decode_utf8;
	my $value = params('input');
	$value = decode_utf8($value);

Decoding UTF-8 is done when filling %input_params hash and $path_info
variable; the former requires to move from explicit $cgi->param(<label>)
to $input_params{<name>} in a few places, which is a good idea anyway.

Also add -override=>1 parameter to $cgi->textfield() invocation in search
form.  Otherwise CGI would use values from query string if it is present,
filling value from $cgi->param... without decode_utf8().  As we are using
value of appropriate parameter anyway, -override=>1 doesn't change the
situation but makes gitweb fill search field correctly.

We could simply use the '-utf8' pragma (via "use CGI '-utf8';") to solve
this, but according to CGI.pm documentation, it may cause problems with
POST requests containing binary files, and it requires CGI 3.31 (I think),
released with perl v5.8.9.

Reported-by: Michał Kiedrowicz <michal.kiedrowicz@gmail.com>
Signed-off-by: Jakub Narębski <jnareb@gmail.com>
Tested-by: Michał Kiedrowicz <michal.kiedrowicz@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -52,7 +52,7 @@ sub evaluate_uri {
 	# as base URL.
 	# Therefore, if we needed to strip PATH_INFO, then we know that we have
 	# to build the base URL ourselves:
-	our $path_info = $ENV{"PATH_INFO"};
+	our $path_info = decode_utf8($ENV{"PATH_INFO"});
 	if ($path_info) {
 		if ($my_url =~ s,\Q$path_info\E$,, &&
 		    $my_uri =~ s,\Q$path_info\E$,, &&
@@ -816,9 +816,9 @@ sub evaluate_query_params {
 
 	while (my ($name, $symbol) = each %cgi_param_mapping) {
 		if ($symbol eq 'opt') {
-			$input_params{$name} = [ $cgi->param($symbol) ];
+			$input_params{$name} = [ map { decode_utf8($_) } $cgi->param($symbol) ];
 		} else {
-			$input_params{$name} = $cgi->param($symbol);
+			$input_params{$name} = decode_utf8($cgi->param($symbol));
 		}
 	}
 }
@@ -2765,7 +2765,7 @@ sub git_populate_project_tagcloud {
 	}
 
 	my $cloud;
-	my $matched = $cgi->param('by_tag');
+	my $matched = $input_params{'ctag'};
 	if (eval { require HTML::TagCloud; 1; }) {
 		$cloud = HTML::TagCloud->new;
 		foreach my $ctag (sort keys %ctags_lc) {
@@ -3871,7 +3871,7 @@ sub print_search_form {
 	                       -values => ['commit', 'grep', 'author', 'committer', 'pickaxe']) .
 	      $cgi->sup($cgi->a({-href => href(action=>"search_help")}, "?")) .
 	      " search:\n",
-	      $cgi->textfield(-name => "s", -value => $searchtext) . "\n" .
+	      $cgi->textfield(-name => "s", -value => $searchtext, -override => 1) . "\n" .
 	      "<span title=\"Extended regular expression\">" .
 	      $cgi->checkbox(-name => 'sr', -value => 1, -label => 're',
 	                     -checked => $search_use_regexp) .
@@ -5280,7 +5280,7 @@ sub git_project_list_body {
 
 	my $check_forks = gitweb_check_feature('forks');
 	my $show_ctags  = gitweb_check_feature('ctags');
-	my $tagfilter = $show_ctags ? $cgi->param('by_tag') : undef;
+	my $tagfilter = $show_ctags ? $input_params{'ctag'} : undef;
 	$check_forks = undef
 		if ($tagfilter || $searchtext);
 
@@ -5992,7 +5992,7 @@ sub git_project_list {
 	}
 	print $cgi->startform(-method => "get") .
 	      "<p class=\"projsearch\">Search:\n" .
-	      $cgi->textfield(-name => "s", -value => $searchtext) . "\n" .
+	      $cgi->textfield(-name => "s", -value => $searchtext, -override => 1) . "\n" .
 	      "</p>" .
 	      $cgi->end_form() . "\n";
 	git_project_list_body(\@list, $order);
@@ -6195,7 +6195,7 @@ sub git_tag {
 
 sub git_blame_common {
 	my $format = shift || 'porcelain';
-	if ($format eq 'porcelain' && $cgi->param('js')) {
+	if ($format eq 'porcelain' && $input_params{'javascript'}) {
 		$format = 'incremental';
 		$action = 'blame_incremental'; # for page title etc
 	}