contrib/diff-highlight/diff-highlight

   1 #!/usr/bin/perl
   2
   3 use warnings FATAL => 'all';
   4 use strict;
   5
   6 # Highlight by reversing foreground and background. You could do
   7 # other things like bold or underline if you prefer.
   8 my $HIGHLIGHT   = "\x1b[7m";
   9 my $UNHIGHLIGHT = "\x1b[27m";
  10 my $COLOR = qr/\x1b\[[0-9;]*m/;
  11 my $BORING = qr/$COLOR|\s/;
  12
  13 my @removed;
  14 my @added;
  15 my $in_hunk;
  16
  17 # Some scripts may not realize that SIGPIPE is being ignored when launching the
  18 # pager--for instance scripts written in Python.
  19 $SIG{PIPE} = 'DEFAULT';
  20
  21 while (<>) {
  22         if (!$in_hunk) {
  23                 print;
  24                 $in_hunk = /^$COLOR*\@/;
  25         }
  26         elsif (/^$COLOR*-/) {
  27                 push @removed, $_;
  28         }
  29         elsif (/^$COLOR*\+/) {
  30                 push @added, $_;
  31         }
  32         else {
  33                 show_hunk(\@removed, \@added);
  34                 @removed = ();
  35                 @added = ();
  36
  37                 print;
  38                 $in_hunk = /^$COLOR*[\@ ]/;
  39         }
  40
  41         # Most of the time there is enough output to keep things streaming,
  42         # but for something like "git log -Sfoo", you can get one early
  43         # commit and then many seconds of nothing. We want to show
  44         # that one commit as soon as possible.
  45         #
  46         # Since we can receive arbitrary input, there's no optimal
  47         # place to flush. Flushing on a blank line is a heuristic that
  48         # happens to match git-log output.
  49         if (!length) {
  50                 local $| = 1;
  51         }
  52 }
  53
  54 # Flush any queued hunk (this can happen when there is no trailing context in
  55 # the final diff of the input).
  56 show_hunk(\@removed, \@added);
  57
  58 exit 0;
  59
  60 sub show_hunk {
  61         my ($a, $b) = @_;
  62
  63         # If one side is empty, then there is nothing to compare or highlight.
  64         if (!@$a || !@$b) {
  65                 print @$a, @$b;
  66                 return;
  67         }
  68
  69         # If we have mismatched numbers of lines on each side, we could try to
  70         # be clever and match up similar lines. But for now we are simple and
  71         # stupid, and only handle multi-line hunks that remove and add the same
  72         # number of lines.
  73         if (@$a != @$b) {
  74                 print @$a, @$b;
  75                 return;
  76         }
  77
  78         my @queue;
  79         for (my $i = 0; $i < @$a; $i++) {
  80                 my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
  81                 print $rm;
  82                 push @queue, $add;
  83         }
  84         print @queue;
  85 }
  86
  87 sub highlight_pair {
  88         my @a = split_line(shift);
  89         my @b = split_line(shift);
  90
  91         # Find common prefix, taking care to skip any ansi
  92         # color codes.
  93         my $seen_plusminus;
  94         my ($pa, $pb) = (0, 0);
  95         while ($pa < @a && $pb < @b) {
  96                 if ($a[$pa] =~ /$COLOR/) {
  97                         $pa++;
  98                 }
  99                 elsif ($b[$pb] =~ /$COLOR/) {
 100                         $pb++;
 101                 }
 102                 elsif ($a[$pa] eq $b[$pb]) {
 103                         $pa++;
 104                         $pb++;
 105                 }
 106                 elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
 107                         $seen_plusminus = 1;
 108                         $pa++;
 109                         $pb++;
 110                 }
 111                 else {
 112                         last;
 113                 }
 114         }
 115
 116         # Find common suffix, ignoring colors.
 117         my ($sa, $sb) = ($#a, $#b);
 118         while ($sa >= $pa && $sb >= $pb) {
 119                 if ($a[$sa] =~ /$COLOR/) {
 120                         $sa--;
 121                 }
 122                 elsif ($b[$sb] =~ /$COLOR/) {
 123                         $sb--;
 124                 }
 125                 elsif ($a[$sa] eq $b[$sb]) {
 126                         $sa--;
 127                         $sb--;
 128                 }
 129                 else {
 130                         last;
 131                 }
 132         }
 133
 134         if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) {
 135                 return highlight_line(\@a, $pa, $sa),
 136                        highlight_line(\@b, $pb, $sb);
 137         }
 138         else {
 139                 return join('', @a),
 140                        join('', @b);
 141         }
 142 }
 143
 144 sub split_line {
 145         local $_ = shift;
 146         return map { /$COLOR/ ? $_ : (split //) }
 147                split /($COLOR*)/;
 148 }
 149
 150 sub highlight_line {
 151         my ($line, $prefix, $suffix) = @_;
 152
 153         return join('',
 154                 @{$line}[0..($prefix-1)],
 155                 $HIGHLIGHT,
 156                 @{$line}[$prefix..$suffix],
 157                 $UNHIGHLIGHT,
 158                 @{$line}[($suffix+1)..$#$line]
 159         );
 160 }
 161
 162 # Pairs are interesting to highlight only if we are going to end up
 163 # highlighting a subset (i.e., not the whole line). Otherwise, the highlighting
 164 # is just useless noise. We can detect this by finding either a matching prefix
 165 # or suffix (disregarding boring bits like whitespace and colorization).
 166 sub is_pair_interesting {
 167         my ($a, $pa, $sa, $b, $pb, $sb) = @_;
 168         my $prefix_a = join('', @$a[0..($pa-1)]);
 169         my $prefix_b = join('', @$b[0..($pb-1)]);
 170         my $suffix_a = join('', @$a[($sa+1)..$#$a]);
 171         my $suffix_b = join('', @$b[($sb+1)..$#$b]);
 172
 173         return $prefix_a !~ /^$COLOR*-$BORING*$/ ||
 174                $prefix_b !~ /^$COLOR*\+$BORING*$/ ||
 175                $suffix_a !~ /^$BORING*$/ ||
 176                $suffix_b !~ /^$BORING*$/;
 177 }