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 # The patch portion of git log -p --graph should only ever have preceding | and
  25 # not / or \ as merge history only shows up on the commit line.
  26 my $GRAPH = qr/$COLOR?\|$COLOR?\s+/;
  27
  28 my @removed;
  29 my @added;
  30 my $in_hunk;
  31
  32 # Some scripts may not realize that SIGPIPE is being ignored when launching the
  33 # pager--for instance scripts written in Python.
  34 $SIG{PIPE} = 'DEFAULT';
  35
  36 while (<>) {
  37         if (!$in_hunk) {
  38                 print;
  39                 $in_hunk = /^$GRAPH*$COLOR*\@\@ /;
  40         }
  41         elsif (/^$GRAPH*$COLOR*-/) {
  42                 push @removed, $_;
  43         }
  44         elsif (/^$GRAPH*$COLOR*\+/) {
  45                 push @added, $_;
  46         }
  47         else {
  48                 show_hunk(\@removed, \@added);
  49                 @removed = ();
  50                 @added = ();
  51
  52                 print;
  53                 $in_hunk = /^$GRAPH*$COLOR*[\@ ]/;
  54         }
  55
  56         # Most of the time there is enough output to keep things streaming,
  57         # but for something like "git log -Sfoo", you can get one early
  58         # commit and then many seconds of nothing. We want to show
  59         # that one commit as soon as possible.
  60         #
  61         # Since we can receive arbitrary input, there's no optimal
  62         # place to flush. Flushing on a blank line is a heuristic that
  63         # happens to match git-log output.
  64         if (!length) {
  65                 local $| = 1;
  66         }
  67 }
  68
  69 # Flush any queued hunk (this can happen when there is no trailing context in
  70 # the final diff of the input).
  71 show_hunk(\@removed, \@added);
  72
  73 exit 0;
  74
  75 # Ideally we would feed the default as a human-readable color to
  76 # git-config as the fallback value. But diff-highlight does
  77 # not otherwise depend on git at all, and there are reports
  78 # of it being used in other settings. Let's handle our own
  79 # fallback, which means we will work even if git can't be run.
  80 sub color_config {
  81         my ($key, $default) = @_;
  82         my $s = `git config --get-color $key 2>/dev/null`;
  83         return length($s) ? $s : $default;
  84 }
  85
  86 sub show_hunk {
  87         my ($a, $b) = @_;
  88
  89         # If one side is empty, then there is nothing to compare or highlight.
  90         if (!@$a || !@$b) {
  91                 print @$a, @$b;
  92                 return;
  93         }
  94
  95         # If we have mismatched numbers of lines on each side, we could try to
  96         # be clever and match up similar lines. But for now we are simple and
  97         # stupid, and only handle multi-line hunks that remove and add the same
  98         # number of lines.
  99         if (@$a != @$b) {
 100                 print @$a, @$b;
 101                 return;
 102         }
 103
 104         my @queue;
 105         for (my $i = 0; $i < @$a; $i++) {
 106                 my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
 107                 print $rm;
 108                 push @queue, $add;
 109         }
 110         print @queue;
 111 }
 112
 113 sub highlight_pair {
 114         my @a = split_line(shift);
 115         my @b = split_line(shift);
 116
 117         # Find common prefix, taking care to skip any ansi
 118         # color codes.
 119         my $seen_plusminus;
 120         my ($pa, $pb) = (0, 0);
 121         while ($pa < @a && $pb < @b) {
 122                 if ($a[$pa] =~ /$COLOR/) {
 123                         $pa++;
 124                 }
 125                 elsif ($b[$pb] =~ /$COLOR/) {
 126                         $pb++;
 127                 }
 128                 elsif ($a[$pa] eq $b[$pb]) {
 129                         $pa++;
 130                         $pb++;
 131                 }
 132                 elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
 133                         $seen_plusminus = 1;
 134                         $pa++;
 135                         $pb++;
 136                 }
 137                 else {
 138                         last;
 139                 }
 140         }
 141
 142         # Find common suffix, ignoring colors.
 143         my ($sa, $sb) = ($#a, $#b);
 144         while ($sa >= $pa && $sb >= $pb) {
 145                 if ($a[$sa] =~ /$COLOR/) {
 146                         $sa--;
 147                 }
 148                 elsif ($b[$sb] =~ /$COLOR/) {
 149                         $sb--;
 150                 }
 151                 elsif ($a[$sa] eq $b[$sb]) {
 152                         $sa--;
 153                         $sb--;
 154                 }
 155                 else {
 156                         last;
 157                 }
 158         }
 159
 160         if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) {
 161                 return highlight_line(\@a, $pa, $sa, \@OLD_HIGHLIGHT),
 162                        highlight_line(\@b, $pb, $sb, \@NEW_HIGHLIGHT);
 163         }
 164         else {
 165                 return join('', @a),
 166                        join('', @b);
 167         }
 168 }
 169
 170 # we split either by $COLOR or by character. This has the side effect of
 171 # leaving in graph cruft. It works because the graph cruft does not contain "-"
 172 # or "+"
 173 sub split_line {
 174         local $_ = shift;
 175         return utf8::decode($_) ?
 176                 map { utf8::encode($_); $_ }
 177                         map { /$COLOR/ ? $_ : (split //) }
 178                         split /($COLOR+)/ :
 179                 map { /$COLOR/ ? $_ : (split //) }
 180                 split /($COLOR+)/;
 181 }
 182
 183 sub highlight_line {
 184         my ($line, $prefix, $suffix, $theme) = @_;
 185
 186         my $start = join('', @{$line}[0..($prefix-1)]);
 187         my $mid = join('', @{$line}[$prefix..$suffix]);
 188         my $end = join('', @{$line}[($suffix+1)..$#$line]);
 189
 190         # If we have a "normal" color specified, then take over the whole line.
 191         # Otherwise, we try to just manipulate the highlighted bits.
 192         if (defined $theme->[0]) {
 193                 s/$COLOR//g for ($start, $mid, $end);
 194                 chomp $end;
 195                 return join('',
 196                         $theme->[0], $start, $RESET,
 197                         $theme->[1], $mid, $RESET,
 198                         $theme->[0], $end, $RESET,
 199                         "\n"
 200                 );
 201         } else {
 202                 return join('',
 203                         $start,
 204                         $theme->[1], $mid, $theme->[2],
 205                         $end
 206                 );
 207         }
 208 }
 209
 210 # Pairs are interesting to highlight only if we are going to end up
 211 # highlighting a subset (i.e., not the whole line). Otherwise, the highlighting
 212 # is just useless noise. We can detect this by finding either a matching prefix
 213 # or suffix (disregarding boring bits like whitespace and colorization).
 214 sub is_pair_interesting {
 215         my ($a, $pa, $sa, $b, $pb, $sb) = @_;
 216         my $prefix_a = join('', @$a[0..($pa-1)]);
 217         my $prefix_b = join('', @$b[0..($pb-1)]);
 218         my $suffix_a = join('', @$a[($sa+1)..$#$a]);
 219         my $suffix_b = join('', @$b[($sb+1)..$#$b]);
 220
 221         return $prefix_a !~ /^$GRAPH*$COLOR*-$BORING*$/ ||
 222                $prefix_b !~ /^$GRAPH*$COLOR*\+$BORING*$/ ||
 223                $suffix_a !~ /^$BORING*$/ ||
 224                $suffix_b !~ /^$BORING*$/;
 225 }