contrib/diff-highlight/diff-highlight

   1 #!/usr/bin/perl
   2
   3 use 5.008;
   4 use warnings FATAL => 'all';
   5 use strict;
   6
   7 # Highlight by reversing foreground and background. You could do
   8 # other things like bold or underline if you prefer.
   9 my @OLD_HIGHLIGHT = (
  10         color_config('color.diff-highlight.oldnormal'),
  11         color_config('color.diff-highlight.oldhighlight', "\x1b[7m"),
  12         color_config('color.diff-highlight.oldreset', "\x1b[27m")
  13 );
  14 my @NEW_HIGHLIGHT = (
  15         color_config('color.diff-highlight.newnormal', $OLD_HIGHLIGHT[0]),
  16         color_config('color.diff-highlight.newhighlight', $OLD_HIGHLIGHT[1]),
  17         color_config('color.diff-highlight.newreset', $OLD_HIGHLIGHT[2])
  18 );
  19
  20 my $RESET = "\x1b[m";
  21 my $COLOR = qr/\x1b\[[0-9;]*m/;
  22 my $BORING = qr/$COLOR|\s/;
  23
  24 my @removed;
  25 my @added;
  26 my $in_hunk;
  27
  28 # Some scripts may not realize that SIGPIPE is being ignored when launching the
  29 # pager--for instance scripts written in Python.
  30 $SIG{PIPE} = 'DEFAULT';
  31
  32 while (<>) {
  33         if (!$in_hunk) {
  34                 print;
  35                 $in_hunk = /^$COLOR*\@/;
  36         }
  37         elsif (/^$COLOR*-/) {
  38                 push @removed, $_;
  39         }
  40         elsif (/^$COLOR*\+/) {
  41                 push @added, $_;
  42         }
  43         else {
  44                 show_hunk(\@removed, \@added);
  45                 @removed = ();
  46                 @added = ();
  47
  48                 print;
  49                 $in_hunk = /^$COLOR*[\@ ]/;
  50         }
  51
  52         # Most of the time there is enough output to keep things streaming,
  53         # but for something like "git log -Sfoo", you can get one early
  54         # commit and then many seconds of nothing. We want to show
  55         # that one commit as soon as possible.
  56         #
  57         # Since we can receive arbitrary input, there's no optimal
  58         # place to flush. Flushing on a blank line is a heuristic that
  59         # happens to match git-log output.
  60         if (!length) {
  61                 local $| = 1;
  62         }
  63 }
  64
  65 # Flush any queued hunk (this can happen when there is no trailing context in
  66 # the final diff of the input).
  67 show_hunk(\@removed, \@added);
  68
  69 exit 0;
  70
  71 # Ideally we would feed the default as a human-readable color to
  72 # git-config as the fallback value. But diff-highlight does
  73 # not otherwise depend on git at all, and there are reports
  74 # of it being used in other settings. Let's handle our own
  75 # fallback, which means we will work even if git can't be run.
  76 sub color_config {
  77         my ($key, $default) = @_;
  78         my $s = `git config --get-color $key 2>/dev/null`;
  79         return length($s) ? $s : $default;
  80 }
  81
  82 sub show_hunk {
  83         my ($a, $b) = @_;
  84
  85         # If one side is empty, then there is nothing to compare or highlight.
  86         if (!@$a || !@$b) {
  87                 print @$a, @$b;
  88                 return;
  89         }
  90
  91         # If we have mismatched numbers of lines on each side, we could try to
  92         # be clever and match up similar lines. But for now we are simple and
  93         # stupid, and only handle multi-line hunks that remove and add the same
  94         # number of lines.
  95         if (@$a != @$b) {
  96                 print @$a, @$b;
  97                 return;
  98         }
  99
 100         my @queue;
 101         for (my $i = 0; $i < @$a; $i++) {
 102                 my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
 103                 print $rm;
 104                 push @queue, $add;
 105         }
 106         print @queue;
 107 }
 108
 109 sub highlight_pair {
 110         my @a = split_line(shift);
 111         my @b = split_line(shift);
 112
 113         # Find common prefix, taking care to skip any ansi
 114         # color codes.
 115         my $seen_plusminus;
 116         my ($pa, $pb) = (0, 0);
 117         while ($pa < @a && $pb < @b) {
 118                 if ($a[$pa] =~ /$COLOR/) {
 119                         $pa++;
 120                 }
 121                 elsif ($b[$pb] =~ /$COLOR/) {
 122                         $pb++;
 123                 }
 124                 elsif ($a[$pa] eq $b[$pb]) {
 125                         $pa++;
 126                         $pb++;
 127                 }
 128                 elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
 129                         $seen_plusminus = 1;
 130                         $pa++;
 131                         $pb++;
 132                 }
 133                 else {
 134                         last;
 135                 }
 136         }
 137
 138         # Find common suffix, ignoring colors.
 139         my ($sa, $sb) = ($#a, $#b);
 140         while ($sa >= $pa && $sb >= $pb) {
 141                 if ($a[$sa] =~ /$COLOR/) {
 142                         $sa--;
 143                 }
 144                 elsif ($b[$sb] =~ /$COLOR/) {
 145                         $sb--;
 146                 }
 147                 elsif ($a[$sa] eq $b[$sb]) {
 148                         $sa--;
 149                         $sb--;
 150                 }
 151                 else {
 152                         last;
 153                 }
 154         }
 155
 156         if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) {
 157                 return highlight_line(\@a, $pa, $sa, \@OLD_HIGHLIGHT),
 158                        highlight_line(\@b, $pb, $sb, \@NEW_HIGHLIGHT);
 159         }
 160         else {
 161                 return join('', @a),
 162                        join('', @b);
 163         }
 164 }
 165
 166 sub split_line {
 167         local $_ = shift;
 168         return utf8::decode($_) ?
 169                 map { utf8::encode($_); $_ }
 170                         map { /$COLOR/ ? $_ : (split //) }
 171                         split /($COLOR+)/ :
 172                 map { /$COLOR/ ? $_ : (split //) }
 173                 split /($COLOR+)/;
 174 }
 175
 176 sub highlight_line {
 177         my ($line, $prefix, $suffix, $theme) = @_;
 178
 179         my $start = join('', @{$line}[0..($prefix-1)]);
 180         my $mid = join('', @{$line}[$prefix..$suffix]);
 181         my $end = join('', @{$line}[($suffix+1)..$#$line]);
 182
 183         # If we have a "normal" color specified, then take over the whole line.
 184         # Otherwise, we try to just manipulate the highlighted bits.
 185         if (defined $theme->[0]) {
 186                 s/$COLOR//g for ($start, $mid, $end);
 187                 chomp $end;
 188                 return join('',
 189                         $theme->[0], $start, $RESET,
 190                         $theme->[1], $mid, $RESET,
 191                         $theme->[0], $end, $RESET,
 192                         "\n"
 193                 );
 194         } else {
 195                 return join('',
 196                         $start,
 197                         $theme->[1], $mid, $theme->[2],
 198                         $end
 199                 );
 200         }
 201 }
 202
 203 # Pairs are interesting to highlight only if we are going to end up
 204 # highlighting a subset (i.e., not the whole line). Otherwise, the highlighting
 205 # is just useless noise. We can detect this by finding either a matching prefix
 206 # or suffix (disregarding boring bits like whitespace and colorization).
 207 sub is_pair_interesting {
 208         my ($a, $pa, $sa, $b, $pb, $sb) = @_;
 209         my $prefix_a = join('', @$a[0..($pa-1)]);
 210         my $prefix_b = join('', @$b[0..($pb-1)]);
 211         my $suffix_a = join('', @$a[($sa+1)..$#$a]);
 212         my $suffix_b = join('', @$b[($sb+1)..$#$b]);
 213
 214         return $prefix_a !~ /^$COLOR*-$BORING*$/ ||
 215                $prefix_b !~ /^$COLOR*\+$BORING*$/ ||
 216                $suffix_a !~ /^$BORING*$/ ||
 217                $suffix_b !~ /^$BORING*$/;
 218 }