Merge branch 'mk/gitweb-diff-hl'

"gitweb" learns to highlight the patch it outputs even more.

By Michał Kiedrowicz (7) and Jakub Narębski (1)
* mk/gitweb-diff-hl:
  gitweb: Refinement highlightning in combined diffs
  gitweb: Highlight interesting parts of diff
  gitweb: Push formatting diff lines to print_diff_chunk()
  gitweb: Use print_diff_chunk() for both side-by-side and inline diffs
  gitweb: Extract print_sidebyside_diff_lines()
  gitweb: Pass esc_html_hl_regions() options to esc_html()
  gitweb: esc_html_hl_regions(): Don't create empty <span> elements
  gitweb: Use descriptive names in esc_html_hl_regions()

2 files changed, 244 insertions, 87 deletions

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 4171de86e3..49a2ec6c0f 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -1732,20 +1732,29 @@ sub chop_and_escape_str {
 # '<span class="mark">foo</span>bar'
 sub esc_html_hl_regions {
 	my ($str, $css_class, @sel) = @_;
-	return esc_html($str) unless @sel;
+	my %opts = grep { ref($_) ne 'ARRAY' } @sel;
+	@sel     = grep { ref($_) eq 'ARRAY' } @sel;
+	return esc_html($str, %opts) unless @sel;
 
 	my $out = '';
 	my $pos = 0;
 
 	for my $s (@sel) {
-		$out .= esc_html(substr($str, $pos, $s->[0] - $pos))
-			if ($s->[0] - $pos > 0);
-		$out .= $cgi->span({-class => $css_class},
-		                   esc_html(substr($str, $s->[0], $s->[1] - $s->[0])));
+		my ($begin, $end) = @$s;
 
-		$pos = $s->[1];
+		# Don't create empty <span> elements.
+		next if $end <= $begin;
+
+		my $escaped = esc_html(substr($str, $begin, $end - $begin),
+		                       %opts);
+
+		$out .= esc_html(substr($str, $pos, $begin - $pos), %opts)
+			if ($begin - $pos > 0);
+		$out .= $cgi->span({-class => $css_class}, $escaped);
+
+		$pos = $end;
 	}
-	$out .= esc_html(substr($str, $pos))
+	$out .= esc_html(substr($str, $pos), %opts)
 		if ($pos < length($str));
 
 	return $out;
@@ -2421,26 +2430,32 @@ sub format_cc_diff_chunk_header {
 }
 
 # process patch (diff) line (not to be used for diff headers),
-# returning class and HTML-formatted (but not wrapped) line
-sub process_diff_line {
-	my $line = shift;
-	my ($from, $to) = @_;
-
-	my $diff_class = diff_line_class($line, $from, $to);
-
-	chomp $line;
-	$line = untabify($line);
+# returning HTML-formatted (but not wrapped) line.
+# If the line is passed as a reference, it is treated as HTML and not
+# esc_html()'ed.
+sub format_diff_line {
+	my ($line, $diff_class, $from, $to) = @_;
+
+	if (ref($line)) {
+		$line = $$line;
+	} else {
+		chomp $line;
+		$line = untabify($line);
 
-	if ($from && $to && $line =~ m/^\@{2} /) {
-		$line = format_unidiff_chunk_header($line, $from, $to);
-		return $diff_class, $line;
+		if ($from && $to && $line =~ m/^\@{2} /) {
+			$line = format_unidiff_chunk_header($line, $from, $to);
+		} elsif ($from && $to && $line =~ m/^\@{3}/) {
+			$line = format_cc_diff_chunk_header($line, $from, $to);
+		} else {
+			$line = esc_html($line, -nbsp=>1);
+		}
+	}
 
-	} elsif ($from && $to && $line =~ m/^\@{3}/) {
-		$line = format_cc_diff_chunk_header($line, $from, $to);
-		return $diff_class, $line;
+	my $diff_classes = "diff";
+	$diff_classes .= " $diff_class" if ($diff_class);
+	$line = "<div class=\"$diff_classes\">$line</div>\n";
 
-	}
-	return $diff_class, esc_html($line, -nbsp=>1);
+	return $line;
 }
 
 # Generates undef or something like "_snapshot_" or "snapshot (_tbz2_ _zip_)",
@@ -4994,10 +5009,186 @@ sub git_difftree_body {
 	print "</table>\n";
 }
 
-sub print_sidebyside_diff_chunk {
-	my @chunk = @_;
+# Print context lines and then rem/add lines in a side-by-side manner.
+sub print_sidebyside_diff_lines {
+	my ($ctx, $rem, $add) = @_;
+
+	# print context block before add/rem block
+	if (@$ctx) {
+		print join '',
+			'<div class="chunk_block ctx">',
+				'<div class="old">',
+				@$ctx,
+				'</div>',
+				'<div class="new">',
+				@$ctx,
+				'</div>',
+			'</div>';
+	}
+
+	if (!@$add) {
+		# pure removal
+		print join '',
+			'<div class="chunk_block rem">',
+				'<div class="old">',
+				@$rem,
+				'</div>',
+			'</div>';
+	} elsif (!@$rem) {
+		# pure addition
+		print join '',
+			'<div class="chunk_block add">',
+				'<div class="new">',
+				@$add,
+				'</div>',
+			'</div>';
+	} else {
+		print join '',
+			'<div class="chunk_block chg">',
+				'<div class="old">',
+				@$rem,
+				'</div>',
+				'<div class="new">',
+				@$add,
+				'</div>',
+			'</div>';
+	}
+}
+
+# Print context lines and then rem/add lines in inline manner.
+sub print_inline_diff_lines {
+	my ($ctx, $rem, $add) = @_;
+
+	print @$ctx, @$rem, @$add;
+}
+
+# Format removed and added line, mark changed part and HTML-format them.
+# Implementation is based on contrib/diff-highlight
+sub format_rem_add_lines_pair {
+	my ($rem, $add, $num_parents) = @_;
+
+	# We need to untabify lines before split()'ing them;
+	# otherwise offsets would be invalid.
+	chomp $rem;
+	chomp $add;
+	$rem = untabify($rem);
+	$add = untabify($add);
+
+	my @rem = split(//, $rem);
+	my @add = split(//, $add);
+	my ($esc_rem, $esc_add);
+	# Ignore leading +/- characters for each parent.
+	my ($prefix_len, $suffix_len) = ($num_parents, 0);
+	my ($prefix_has_nonspace, $suffix_has_nonspace);
+
+	my $shorter = (@rem < @add) ? @rem : @add;
+	while ($prefix_len < $shorter) {
+		last if ($rem[$prefix_len] ne $add[$prefix_len]);
+
+		$prefix_has_nonspace = 1 if ($rem[$prefix_len] !~ /\s/);
+		$prefix_len++;
+	}
+
+	while ($prefix_len + $suffix_len < $shorter) {
+		last if ($rem[-1 - $suffix_len] ne $add[-1 - $suffix_len]);
+
+		$suffix_has_nonspace = 1 if ($rem[-1 - $suffix_len] !~ /\s/);
+		$suffix_len++;
+	}
+
+	# Mark lines that are different from each other, but have some common
+	# part that isn't whitespace.  If lines are completely different, don't
+	# mark them because that would make output unreadable, especially if
+	# diff consists of multiple lines.
+	if ($prefix_has_nonspace || $suffix_has_nonspace) {
+		$esc_rem = esc_html_hl_regions($rem, 'marked',
+		        [$prefix_len, @rem - $suffix_len], -nbsp=>1);
+		$esc_add = esc_html_hl_regions($add, 'marked',
+		        [$prefix_len, @add - $suffix_len], -nbsp=>1);
+	} else {
+		$esc_rem = esc_html($rem, -nbsp=>1);
+		$esc_add = esc_html($add, -nbsp=>1);
+	}
+
+	return format_diff_line(\$esc_rem, 'rem'),
+	       format_diff_line(\$esc_add, 'add');
+}
+
+# HTML-format diff context, removed and added lines.
+sub format_ctx_rem_add_lines {
+	my ($ctx, $rem, $add, $num_parents) = @_;
+	my (@new_ctx, @new_rem, @new_add);
+	my $can_highlight = 0;
+	my $is_combined = ($num_parents > 1);
+
+	# Highlight if every removed line has a corresponding added line.
+	if (@$add > 0 && @$add == @$rem) {
+		$can_highlight = 1;
+
+		# Highlight lines in combined diff only if the chunk contains
+		# diff between the same version, e.g.
+		#
+		#    - a
+		#   -  b
+		#    + c
+		#   +  d
+		#
+		# Otherwise the highlightling would be confusing.
+		if ($is_combined) {
+			for (my $i = 0; $i < @$add; $i++) {
+				my $prefix_rem = substr($rem->[$i], 0, $num_parents);
+				my $prefix_add = substr($add->[$i], 0, $num_parents);
+
+				$prefix_rem =~ s/-/+/g;
+
+				if ($prefix_rem ne $prefix_add) {
+					$can_highlight = 0;
+					last;
+				}
+			}
+		}
+	}
+
+	if ($can_highlight) {
+		for (my $i = 0; $i < @$add; $i++) {
+			my ($line_rem, $line_add) = format_rem_add_lines_pair(
+			        $rem->[$i], $add->[$i], $num_parents);
+			push @new_rem, $line_rem;
+			push @new_add, $line_add;
+		}
+	} else {
+		@new_rem = map { format_diff_line($_, 'rem') } @$rem;
+		@new_add = map { format_diff_line($_, 'add') } @$add;
+	}
+
+	@new_ctx = map { format_diff_line($_, 'ctx') } @$ctx;
+
+	return (\@new_ctx, \@new_rem, \@new_add);
+}
+
+# Print context lines and then rem/add lines.
+sub print_diff_lines {
+	my ($ctx, $rem, $add, $diff_style, $num_parents) = @_;
+	my $is_combined = $num_parents > 1;
+
+	($ctx, $rem, $add) = format_ctx_rem_add_lines($ctx, $rem, $add,
+	        $num_parents);
+
+	if ($diff_style eq 'sidebyside' && !$is_combined) {
+		print_sidebyside_diff_lines($ctx, $rem, $add);
+	} else {
+		# default 'inline' style and unknown styles
+		print_inline_diff_lines($ctx, $rem, $add);
+	}
+}
+
+sub print_diff_chunk {
+	my ($diff_style, $num_parents, $from, $to, @chunk) = @_;
 	my (@ctx, @rem, @add);
 
+	# The class of the previous line.
+	my $prev_class = '';
+
 	return unless @chunk;
 
 	# incomplete last line might be among removed or added lines,
@@ -5016,55 +5207,19 @@ sub print_sidebyside_diff_chunk {
 
 		# print chunk headers
 		if ($class && $class eq 'chunk_header') {
-			print $line;
+			print format_diff_line($line, $class, $from, $to);
 			next;
 		}
 
-		## print from accumulator when type of class of lines change
-		# empty contents block on start rem/add block, or end of chunk
-		if (@ctx && (!$class || $class eq 'rem' || $class eq 'add')) {
-			print join '',
-				'<div class="chunk_block ctx">',
-					'<div class="old">',
-					@ctx,
-					'</div>',
-					'<div class="new">',
-					@ctx,
-					'</div>',
-				'</div>';
-			@ctx = ();
-		}
-		# empty add/rem block on start context block, or end of chunk
-		if ((@rem || @add) && (!$class || $class eq 'ctx')) {
-			if (!@add) {
-				# pure removal
-				print join '',
-					'<div class="chunk_block rem">',
-						'<div class="old">',
-						@rem,
-						'</div>',
-					'</div>';
-			} elsif (!@rem) {
-				# pure addition
-				print join '',
-					'<div class="chunk_block add">',
-						'<div class="new">',
-						@add,
-						'</div>',
-					'</div>';
-			} else {
-				# assume that it is change
-				print join '',
-					'<div class="chunk_block chg">',
-						'<div class="old">',
-						@rem,
-						'</div>',
-						'<div class="new">',
-						@add,
-						'</div>',
-					'</div>';
-			}
-			@rem = @add = ();
+		## print from accumulator when have some add/rem lines or end
+		# of chunk (flush context lines), or when have add and rem
+		# lines and new block is reached (otherwise add/rem lines could
+		# be reordered)
+		if (!$class || ((@rem || @add) && $class eq 'ctx') ||
+		    (@rem && @add && $class ne $prev_class)) {
+			print_diff_lines(\@ctx, \@rem, \@add,
+		                         $diff_style, $num_parents);
+			@ctx = @rem = @add = ();
 		}
 
 		## adding lines to accumulator
@@ -5080,6 +5235,8 @@ sub print_sidebyside_diff_chunk {
 		if ($class eq 'ctx') {
 			push @ctx, $line;
 		}
+
+		$prev_class = $class;
 	}
 }
 
@@ -5201,27 +5358,19 @@ sub git_patchset_body {
 
 			next PATCH if ($patch_line =~ m/^diff /);
 
-			my ($class, $line) = process_diff_line($patch_line, \%from, \%to);
-			my $diff_classes = "diff";
-			$diff_classes .= " $class" if ($class);
-			$line = "<div class=\"$diff_classes\">$line</div>\n";
+			my $class = diff_line_class($patch_line, \%from, \%to);
 
-			if ($diff_style eq 'sidebyside' && !$is_combined) {
-				if ($class eq 'chunk_header') {
-					print_sidebyside_diff_chunk(@chunk);
-					@chunk = ( [ $class, $line ] );
-				} else {
-					push @chunk, [ $class, $line ];
-				}
-			} else {
-				# default 'inline' style and unknown styles
-				print $line;
+			if ($class eq 'chunk_header') {
+				print_diff_chunk($diff_style, scalar @hash_parents, \%from, \%to, @chunk);
+				@chunk = ();
 			}
+
+			push @chunk, [ $class, $patch_line ];
 		}
 
 	} continue {
 		if (@chunk) {
-			print_sidebyside_diff_chunk(@chunk);
+			print_diff_chunk($diff_style, scalar @hash_parents, \%from, \%to, @chunk);
 			@chunk = ();
 		}
 		print "</div>\n"; # class="patch"
diff --git a/gitweb/static/gitweb.css b/gitweb/static/gitweb.css
index c530355a7c..cb86d2d029 100644
--- a/gitweb/static/gitweb.css
+++ b/gitweb/static/gitweb.css
@@ -438,6 +438,10 @@ div.diff.add {
 	color: #008800;
 }
 
+div.diff.add span.marked {
+	background-color: #aaffaa;
+}
+
 div.diff.from_file a.path,
 div.diff.from_file {
 	color: #aa0000;
@@ -447,6 +451,10 @@ div.diff.rem {
 	color: #cc0000;
 }
 
+div.diff.rem span.marked {
+	background-color: #ffaaaa;
+}
+
 div.diff.chunk_header a,
 div.diff.chunk_header {
 	color: #990099;