contrib / diff-highlight / DiffHighlight.pmon commit Merge branch 'ks/branch-set-upstream' (4229478)
   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}