gitweb: Highlight interesting parts of diff

Reading diff output is sometimes very hard, even if it's colored,
especially if lines differ only in few characters.  This is often true
when a commit fixes a typo or renames some variables or functions.

This commit teaches gitweb to highlight characters that are different
between old and new line with a light green/red background.  This should
work in the similar manner as in Trac or GitHub.

The algorithm that compares lines is based on contrib/diff-highlight.
Basically, it works by determining common prefix/suffix of corresponding
lines and highlightning only the middle part of lines.  For more
information, see contrib/diff-highlight/README.

Combined diffs are not supported but a following commit will change it.

Since we need to pass esc_html()'ed or esc_html_hl_regions()'ed lines to
format_diff_lines(), so it was taught to accept preformatted lines
passed as a reference.

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

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 390774ed93a01300947171dfba045084188000a8..d5b3f04e118d1b86bf009a163bc9e7ade060b017 100755 (executable)
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -2430,19 +2430,25 @@ sub format_cc_diff_chunk_header {
 }
 
 # process patch (diff) line (not to be used for diff headers),
-# returning HTML-formatted (but not wrapped) 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) = @_;
 
-       chomp $line;
-       $line = untabify($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, $to);
+       if (ref($line)) {
+               $line = $$line;
        } else {
-               $line = esc_html($line, -nbsp=>1);
+               chomp $line;
+               $line = untabify($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);
+               }
        }
 
        my $diff_classes = "diff";
@@ -5055,10 +5061,89 @@ sub print_inline_diff_lines {
        print @$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) = @_;
+
+       # 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 +/- character, thus $prefix_len is set to 1.
+       my ($prefix_len, $suffix_len) = (1, 0);
+       my ($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, $is_combined) = @_;
+       my (@new_ctx, @new_rem, @new_add);
+
+       # Highlight if every removed line has a corresponding added line.
+       # Combined diffs are not supported at this moment.
+       if (!$is_combined && @$add > 0 && @$add == @$rem) {
+               for (my $i = 0; $i < @$add; $i++) {
+                       my ($line_rem, $line_add) = format_rem_add_lines_pair(
+                               $rem->[$i], $add->[$i]);
+                       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, $is_combined) = @_;
 
+       ($ctx, $rem, $add) = format_ctx_rem_add_lines($ctx, $rem, $add,
+               $is_combined);
+
        if ($diff_style eq 'sidebyside' && !$is_combined) {
                print_sidebyside_diff_lines($ctx, $rem, $add);
        } else {
@@ -5090,11 +5175,9 @@ sub print_diff_chunk {
        foreach my $line_info (@chunk) {
                my ($class, $line) = @$line_info;
 
-               $line = format_diff_line($line, $class, $from, $to);
-
                # print chunk headers
                if ($class && $class eq 'chunk_header') {
-                       print $line;
+                       print format_diff_line($line, $class, $from, $to);
                        next;
                }
 

diff --git a/gitweb/static/gitweb.css b/gitweb/static/gitweb.css
index c530355a7cefefe694f8cbdcc3a7acc5725bec3a..cb86d2d029637ec64f70cc9e1cdbeeea972e8771 100644 (file)
--- 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;