gitweb: A bit of code cleanup in git_blame()

Among others, here are the highlights:

 * move variable declaration closer to the place it is set and used,
   if possible,

 * uniquify and simplify coding style a bit, which includes removing
   unnecessary '()'.

 * check type only if $hash was defined, as otherwise from the way
   git_get_hash_by_path() is called (and works), we know that it is
   a blob,

 * use modern calling convention for git-blame,

 * remove unused variable,

 * don't use implicit variables ($_),

 * add some comments

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Acked-by: Luben Tuikov <ltuikov@yahoo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -4575,28 +4575,33 @@ sub git_tag {
 }
 
 sub git_blame {
-	my $fd;
-	my $ftype;
-
+	# permissions
 	gitweb_check_feature('blame')
 		or die_error(403, "Blame view not allowed");
 
+	# error checking
 	die_error(400, "No file name given") unless $file_name;
 	$hash_base ||= git_get_head_hash($project);
-	die_error(404, "Couldn't find base commit") unless ($hash_base);
+	die_error(404, "Couldn't find base commit") unless $hash_base;
 	my %co = parse_commit($hash_base)
 		or die_error(404, "Commit not found");
+	my $ftype = "blob";
 	if (!defined $hash) {
 		$hash = git_get_hash_by_path($hash_base, $file_name, "blob")
 			or die_error(404, "Error looking up file");
-	}
+	} else {
 		$ftype = git_get_type($hash);
 		if ($ftype !~ "blob") {
 			die_error(400, "Object is not a blob");
 		}
-	open ($fd, "-|", git_cmd(), "blame", '-p', '--',
-	      $file_name, $hash_base)
+	}
+
+	# run git-blame --porcelain
+	open my $fd, "-|", git_cmd(), "blame", '-p',
+		$hash_base, '--', $file_name
 		or die_error(500, "Open git-blame failed");
+
+	# page header
 	git_header_html();
 	my $formats_nav =
 		$cgi->a({-href => href(action=>"blob", -replay=>1)},
@@ -4610,40 +4615,44 @@ sub git_blame {
 	git_print_page_nav('','', $hash_base,$co{'tree'},$hash_base, $formats_nav);
 	git_print_header_div('commit', esc_html($co{'title'}), $hash_base);
 	git_print_page_path($file_name, $ftype, $hash_base);
-	my @rev_color = (qw(light2 dark2));
+
+	# page body
+	my @rev_color = qw(light2 dark2);
 	my $num_colors = scalar(@rev_color);
 	my $current_color = 0;
-	my $last_rev;
+	my %metainfo = ();
+
 	print <<HTML;
 <div class="page_body">
 <table class="blame">
 <tr><th>Commit</th><th>Line</th><th>Data</th></tr>
 HTML
-	my %metainfo = ();
-	while (1) {
-		$_ = <$fd>;
-		last unless defined $_;
+ LINE:
+	while (my $line = <$fd>) {
+		chomp $line;
+		# the header: <SHA-1> <src lineno> <dst lineno> [<lines in group>]
+		# no <lines in group> for subsequent lines in group of lines
 		my ($full_rev, $orig_lineno, $lineno, $group_size) =
-		    /^([0-9a-f]{40}) (\d+) (\d+)(?: (\d+))?$/;
+		   ($line =~ /^([0-9a-f]{40}) (\d+) (\d+)(?: (\d+))?$/);
 		if (!exists $metainfo{$full_rev}) {
 			$metainfo{$full_rev} = {};
 		}
 		my $meta = $metainfo{$full_rev};
-		while (<$fd>) {
-			last if (s/^\t//);
-			if (/^(\S+) (.*)$/) {
+		my $data;
+		while ($data = <$fd>) {
+			chomp $data;
+			last if ($data =~ s/^\t//); # contents of line
+			if ($data =~ /^(\S+) (.*)$/) {
 				$meta->{$1} = $2;
 			}
 		}
-		my $data = $_;
-		chomp $data;
-		my $rev = substr($full_rev, 0, 8);
+		my $short_rev = substr($full_rev, 0, 8);
 		my $author = $meta->{'author'};
-		my %date = parse_date($meta->{'author-time'},
-		                      $meta->{'author-tz'});
+		my %date =
+			parse_date($meta->{'author-time'}, $meta->{'author-tz'});
 		my $date = $date{'iso-tz'};
 		if ($group_size) {
-			$current_color = ++$current_color % $num_colors;
+			$current_color = ($current_color + 1) % $num_colors;
 		}
 		print "<tr id=\"l$lineno\" class=\"$rev_color[$current_color]\">\n";
 		if ($group_size) {
@@ -4654,7 +4663,7 @@ HTML
 			print $cgi->a({-href => href(action=>"commit",
 			                             hash=>$full_rev,
 			                             file_name=>$file_name)},
-			              esc_html($rev));
+			              esc_html($short_rev));
 			print "</td>\n";
 		}
 		open (my $dd, "-|", git_cmd(), "rev-parse", "$full_rev^")
@@ -4677,6 +4686,8 @@ HTML
 	print "</div>";
 	close $fd
 		or print "Reading blob failed\n";
+
+	# page footer
 	git_footer_html();
 }