1package DiffHighlight; 2 3use 5.008; 4use warnings FATAL => 'all'; 5use strict; 6 7# Highlight by reversing foreground and background. You could do 8# other things like bold or underline if you prefer. 9my @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); 14my @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 20my $RESET = "\x1b[m"; 21my $COLOR = qr/\x1b\[[0-9;]*m/; 22my $BORING = qr/$COLOR|\s/; 23 24my @removed; 25my @added; 26my $in_hunk; 27my $graph_indent = 0; 28 29our $line_cb = sub { print @_ }; 30our $flush_cb = sub { local $| = 1 }; 31 32# Count the visible width of a string, excluding any terminal color sequences. 33sub visible_width { 34 local $_ = shift; 35 my $ret = 0; 36 while (length) { 37 if (s/^$COLOR//) { 38 # skip colors 39 } elsif (s/^.//) { 40 $ret++; 41 } 42 } 43 return $ret; 44} 45 46# Return a substring of $str, omitting $len visible characters from the 47# beginning, where terminal color sequences do not count as visible. 48sub visible_substr { 49 my ($str, $len) = @_; 50 while ($len > 0) { 51 if ($str =~ s/^$COLOR//) { 52 next 53 } 54 $str =~ s/^.//; 55 $len--; 56 } 57 return $str; 58} 59 60sub handle_line { 61 my $orig = shift; 62 local $_ = $orig; 63 64 # match a graph line that begins a commit 65 if (/^(?:$COLOR?\|$COLOR?[ ])* # zero or more leading "|" with space 66 $COLOR?\*$COLOR?[ ] # a "*" with its trailing space 67 (?:$COLOR?\|$COLOR?[ ])* # zero or more trailing "|" 68 [ ]* # trailing whitespace for merges 69 /x) { 70 my $graph_prefix = $&; 71 72 # We must flush before setting graph indent, since the 73 # new commit may be indented differently from what we 74 # queued. 75 flush(); 76 $graph_indent = visible_width($graph_prefix); 77 78 } elsif ($graph_indent) { 79 if (length($_) < $graph_indent) { 80 $graph_indent = 0; 81 } else { 82 $_ = visible_substr($_, $graph_indent); 83 } 84 } 85 86 if (!$in_hunk) { 87 $line_cb->($orig); 88 $in_hunk = /^$COLOR*\@\@ /; 89 } 90 elsif (/^$COLOR*-/) { 91 push @removed, $orig; 92 } 93 elsif (/^$COLOR*\+/) { 94 push @added, $orig; 95 } 96 else { 97 flush(); 98 $line_cb->($orig); 99 $in_hunk = /^$COLOR*[\@ ]/; 100 } 101 102 # Most of the time there is enough output to keep things streaming, 103 # but for something like "git log -Sfoo", you can get one early 104 # commit and then many seconds of nothing. We want to show 105 # that one commit as soon as possible. 106 # 107 # Since we can receive arbitrary input, there's no optimal 108 # place to flush. Flushing on a blank line is a heuristic that 109 # happens to match git-log output. 110 if (!length) { 111 $flush_cb->(); 112 } 113} 114 115sub flush { 116 # Flush any queued hunk (this can happen when there is no trailing 117 # context in the final diff of the input). 118 show_hunk(\@removed, \@added); 119 @removed = (); 120 @added = (); 121} 122 123sub highlight_stdin { 124 while (<STDIN>) { 125 handle_line($_); 126 } 127 flush(); 128} 129 130# Ideally we would feed the default as a human-readable color to 131# git-config as the fallback value. But diff-highlight does 132# not otherwise depend on git at all, and there are reports 133# of it being used in other settings. Let's handle our own 134# fallback, which means we will work even if git can't be run. 135sub color_config { 136 my ($key, $default) = @_; 137 my $s = `git config --get-color $key 2>/dev/null`; 138 return length($s) ? $s : $default; 139} 140 141sub show_hunk { 142 my ($a, $b) = @_; 143 144 # If one side is empty, then there is nothing to compare or highlight. 145 if (!@$a || !@$b) { 146 $line_cb->(@$a, @$b); 147 return; 148 } 149 150 # If we have mismatched numbers of lines on each side, we could try to 151 # be clever and match up similar lines. But for now we are simple and 152 # stupid, and only handle multi-line hunks that remove and add the same 153 # number of lines. 154 if (@$a != @$b) { 155 $line_cb->(@$a, @$b); 156 return; 157 } 158 159 my @queue; 160 for (my $i = 0; $i < @$a; $i++) { 161 my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]); 162 $line_cb->($rm); 163 push @queue, $add; 164 } 165 $line_cb->(@queue); 166} 167 168sub highlight_pair { 169 my @a = split_line(shift); 170 my @b = split_line(shift); 171 172 # Find common prefix, taking care to skip any ansi 173 # color codes. 174 my $seen_plusminus; 175 my ($pa, $pb) = (0, 0); 176 while ($pa < @a && $pb < @b) { 177 if ($a[$pa] =~ /$COLOR/) { 178 $pa++; 179 } 180 elsif ($b[$pb] =~ /$COLOR/) { 181 $pb++; 182 } 183 elsif ($a[$pa] eq $b[$pb]) { 184 $pa++; 185 $pb++; 186 } 187 elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') { 188 $seen_plusminus = 1; 189 $pa++; 190 $pb++; 191 } 192 else { 193 last; 194 } 195 } 196 197 # Find common suffix, ignoring colors. 198 my ($sa, $sb) = ($#a, $#b); 199 while ($sa >= $pa && $sb >= $pb) { 200 if ($a[$sa] =~ /$COLOR/) { 201 $sa--; 202 } 203 elsif ($b[$sb] =~ /$COLOR/) { 204 $sb--; 205 } 206 elsif ($a[$sa] eq $b[$sb]) { 207 $sa--; 208 $sb--; 209 } 210 else { 211 last; 212 } 213 } 214 215 if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) { 216 return highlight_line(\@a, $pa, $sa, \@OLD_HIGHLIGHT), 217 highlight_line(\@b, $pb, $sb, \@NEW_HIGHLIGHT); 218 } 219 else { 220 return join('', @a), 221 join('', @b); 222 } 223} 224 225# we split either by $COLOR or by character. This has the side effect of 226# leaving in graph cruft. It works because the graph cruft does not contain "-" 227# or "+" 228sub split_line { 229 local $_ = shift; 230 return utf8::decode($_) ? 231 map { utf8::encode($_); $_ } 232 map { /$COLOR/ ? $_ : (split //) } 233 split /($COLOR+)/ : 234 map { /$COLOR/ ? $_ : (split //) } 235 split /($COLOR+)/; 236} 237 238sub highlight_line { 239 my ($line, $prefix, $suffix, $theme) = @_; 240 241 my $start = join('', @{$line}[0..($prefix-1)]); 242 my $mid = join('', @{$line}[$prefix..$suffix]); 243 my $end = join('', @{$line}[($suffix+1)..$#$line]); 244 245 # If we have a "normal" color specified, then take over the whole line. 246 # Otherwise, we try to just manipulate the highlighted bits. 247 if (defined $theme->[0]) { 248 s/$COLOR//g for ($start, $mid, $end); 249 chomp $end; 250 return join('', 251 $theme->[0], $start, $RESET, 252 $theme->[1], $mid, $RESET, 253 $theme->[0], $end, $RESET, 254 "\n" 255 ); 256 } else { 257 return join('', 258 $start, 259 $theme->[1], $mid, $theme->[2], 260 $end 261 ); 262 } 263} 264 265# Pairs are interesting to highlight only if we are going to end up 266# highlighting a subset (i.e., not the whole line). Otherwise, the highlighting 267# is just useless noise. We can detect this by finding either a matching prefix 268# or suffix (disregarding boring bits like whitespace and colorization). 269sub is_pair_interesting { 270 my ($a, $pa, $sa, $b, $pb, $sb) = @_; 271 my $prefix_a = join('', @$a[0..($pa-1)]); 272 my $prefix_b = join('', @$b[0..($pb-1)]); 273 my $suffix_a = join('', @$a[($sa+1)..$#$a]); 274 my $suffix_b = join('', @$b[($sb+1)..$#$b]); 275 276 return visible_substr($prefix_a, $graph_indent) !~ /^$COLOR*-$BORING*$/ || 277 visible_substr($prefix_b, $graph_indent) !~ /^$COLOR*\+$BORING*$/ || 278 $suffix_a !~ /^$BORING*$/ || 279 $suffix_b !~ /^$BORING*$/; 280}