gitweb: Highlight matched part of shortened project description

Previous commit make gitweb use esc_html_match_hl() to mark match in
the _whole_ description of a project when searching projects.

This commit makes gitweb highlight match in _shortened_ description,
based on match in whole description, using esc_html_match_hl_chopped()
subroutine.

If match is in removed (chopped) part, even partially, then trailing
"... " is highlighted.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -1742,20 +1742,61 @@ sub esc_html_hl_regions {
 	return $out;
 }
 
-# highlight match (if any), and escape HTML
-sub esc_html_match_hl {
+# return positions of beginning and end of each match
+sub matchpos_list {
 	my ($str, $regexp) = @_;
-	return esc_html($str) unless defined $regexp;
+	return unless (defined $str && defined $regexp);
 
 	my @matches;
 	while ($str =~ /$regexp/g) {
 		push @matches, [$-[0], $+[0]];
 	}
+	return @matches;
+}
+
+# highlight match (if any), and escape HTML
+sub esc_html_match_hl {
+	my ($str, $regexp) = @_;
+	return esc_html($str) unless defined $regexp;
+
+	my @matches = matchpos_list($str, $regexp);
 	return esc_html($str) unless @matches;
 
 	return esc_html_hl_regions($str, 'match', @matches);
 }
 
+
+# highlight match (if any) of shortened string, and escape HTML
+sub esc_html_match_hl_chopped {
+	my ($str, $chopped, $regexp) = @_;
+	return esc_html_match_hl($str, $regexp) unless defined $chopped;
+
+	my @matches = matchpos_list($str, $regexp);
+	return esc_html($chopped) unless @matches;
+
+	# filter matches so that we mark chopped string
+	my $tail = "... "; # see chop_str
+	unless ($chopped =~ s/\Q$tail\E$//) {
+		$tail = '';
+	}
+	my $chop_len = length($chopped);
+	my $tail_len = length($tail);
+	my @filtered;
+
+	for my $m (@matches) {
+		if ($m->[0] > $chop_len) {
+			push @filtered, [ $chop_len, $chop_len + $tail_len ] if ($tail_len > 0);
+			last;
+		} elsif ($m->[1] > $chop_len) {
+			push @filtered, [ $m->[0], $chop_len + $tail_len ];
+			last;
+		}
+		push @filtered, $m;
+	}
+
+	return esc_html_hl_regions($chopped . $tail, 'match', @filtered);
+}
+
 ## ----------------------------------------------------------------------
 ## functions returning short strings
 
@@ -5405,9 +5446,10 @@ sub git_project_list_rows {
 		      "</td>\n" .
 		      "<td>" . $cgi->a({-href => href(project=>$pr->{'path'}, action=>"summary"),
 		                        -class => "list",
-		                        $search_regexp ? () : -title => $pr->{'descr_long'}},
+		                        -title => $pr->{'descr_long'}},
 		                        $search_regexp
-		                        ? esc_html_match_hl($pr->{'descr_long'}, $search_regexp)
+		                        ? esc_html_match_hl_chopped($pr->{'descr_long'},
+		                                                    $pr->{'descr'}, $search_regexp)
 		                        : esc_html($pr->{'descr'})) .
 		      "</td>\n" .
 		      "<td><i>" . chop_and_escape_str($pr->{'owner'}, 15) . "</i></td>\n";