contrib/diff-highlight/diff-highlight

   1 #!/usr/bin/perl
   2
   3 # Highlight by reversing foreground and background. You could do
   4 # other things like bold or underline if you prefer.
   5 my $HIGHLIGHT   = "\x1b[7m";
   6 my $UNHIGHLIGHT = "\x1b[27m";
   7 my $COLOR = qr/\x1b\[[0-9;]*m/;
   8
   9 my @window;
  10
  11 while (<>) {
  12         # We highlight only single-line changes, so we need
  13         # a 4-line window to make a decision on whether
  14         # to highlight.
  15         push @window, $_;
  16         next if @window < 4;
  17         if ($window[0] =~ /^$COLOR*(\@| )/ &&
  18             $window[1] =~ /^$COLOR*-/ &&
  19             $window[2] =~ /^$COLOR*\+/ &&
  20             $window[3] !~ /^$COLOR*\+/) {
  21                 print shift @window;
  22                 show_pair(shift @window, shift @window);
  23         }
  24         else {
  25                 print shift @window;
  26         }
  27
  28         # Most of the time there is enough output to keep things streaming,
  29         # but for something like "git log -Sfoo", you can get one early
  30         # commit and then many seconds of nothing. We want to show
  31         # that one commit as soon as possible.
  32         #
  33         # Since we can receive arbitrary input, there's no optimal
  34         # place to flush. Flushing on a blank line is a heuristic that
  35         # happens to match git-log output.
  36         if (!length) {
  37                 local $| = 1;
  38         }
  39 }
  40
  41 # Special case a single-line hunk at the end of file.
  42 if (@window == 3 &&
  43     $window[0] =~ /^$COLOR*(\@| )/ &&
  44     $window[1] =~ /^$COLOR*-/ &&
  45     $window[2] =~ /^$COLOR*\+/) {
  46         print shift @window;
  47         show_pair(shift @window, shift @window);
  48 }
  49
  50 # And then flush any remaining lines.
  51 while (@window) {
  52         print shift @window;
  53 }
  54
  55 exit 0;
  56
  57 sub show_pair {
  58         my @a = split_line(shift);
  59         my @b = split_line(shift);
  60
  61         # Find common prefix, taking care to skip any ansi
  62         # color codes.
  63         my $seen_plusminus;
  64         my ($pa, $pb) = (0, 0);
  65         while ($pa < @a && $pb < @b) {
  66                 if ($a[$pa] =~ /$COLOR/) {
  67                         $pa++;
  68                 }
  69                 elsif ($b[$pb] =~ /$COLOR/) {
  70                         $pb++;
  71                 }
  72                 elsif ($a[$pa] eq $b[$pb]) {
  73                         $pa++;
  74                         $pb++;
  75                 }
  76                 elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
  77                         $seen_plusminus = 1;
  78                         $pa++;
  79                         $pb++;
  80                 }
  81                 else {
  82                         last;
  83                 }
  84         }
  85
  86         # Find common suffix, ignoring colors.
  87         my ($sa, $sb) = ($#a, $#b);
  88         while ($sa >= $pa && $sb >= $pb) {
  89                 if ($a[$sa] =~ /$COLOR/) {
  90                         $sa--;
  91                 }
  92                 elsif ($b[$sb] =~ /$COLOR/) {
  93                         $sb--;
  94                 }
  95                 elsif ($a[$sa] eq $b[$sb]) {
  96                         $sa--;
  97                         $sb--;
  98                 }
  99                 else {
 100                         last;
 101                 }
 102         }
 103
 104         print highlight(\@a, $pa, $sa);
 105         print highlight(\@b, $pb, $sb);
 106 }
 107
 108 sub split_line {
 109         local $_ = shift;
 110         return map { /$COLOR/ ? $_ : (split //) }
 111                split /($COLOR*)/;
 112 }
 113
 114 sub highlight {
 115         my ($line, $prefix, $suffix) = @_;
 116
 117         return join('',
 118                 @{$line}[0..($prefix-1)],
 119                 $HIGHLIGHT,
 120                 @{$line}[$prefix..$suffix],
 121                 $UNHIGHLIGHT,
 122                 @{$line}[($suffix+1)..$#$line]
 123         );
 124 }