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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>
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1 parent f4a8102 commit 5fb6ddf67afb3d0dc9b1fce64543f20b28a81b4b @mkiedrowicz mkiedrowicz committed with gitster Apr 11, 2012
Showing with 103 additions and 12 deletions.
  1. +95 −12 gitweb/gitweb.perl
  2. +8 −0 gitweb/static/gitweb.css
View
107 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;
}
View
8 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;

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