dotfiles

diff-highlight (5399B)

---

 #!/usr/bin/perl
 
 use 5.008;
 use warnings FATAL => 'all';
 use strict;
 
 # Highlight by reversing foreground and background. You could do
 # other things like bold or underline if you prefer.
 my @OLD_HIGHLIGHT = (
 	color_config('color.diff-highlight.oldnormal'),
 	color_config('color.diff-highlight.oldhighlight', "\x1b[7m"),
 	color_config('color.diff-highlight.oldreset', "\x1b[27m")
 );
 my @NEW_HIGHLIGHT = (
 	color_config('color.diff-highlight.newnormal', $OLD_HIGHLIGHT[0]),
 	color_config('color.diff-highlight.newhighlight', $OLD_HIGHLIGHT[1]),
 	color_config('color.diff-highlight.newreset', $OLD_HIGHLIGHT[2])
 );
 
 my $RESET = "\x1b[m";
 my $COLOR = qr/\x1b\[[0-9;]*m/;
 my $BORING = qr/$COLOR|\s/;
 
 my @removed;
 my @added;
 my $in_hunk;
 
 # Some scripts may not realize that SIGPIPE is being ignored when launching the
 # pager--for instance scripts written in Python.
 $SIG{PIPE} = 'DEFAULT';
 
 while (<>) {
 	if (!$in_hunk) {
 		print;
 		$in_hunk = /^$COLOR*\@/;
 	}
 	elsif (/^$COLOR*-/) {
 		push @removed, $_;
 	}
 	elsif (/^$COLOR*\+/) {
 		push @added, $_;
 	}
 	else {
 		show_hunk(\@removed, \@added);
 		@removed = ();
 		@added = ();
 
 		print;
 		$in_hunk = /^$COLOR*[\@ ]/;
 	}
 
 	# Most of the time there is enough output to keep things streaming,
 	# but for something like "git log -Sfoo", you can get one early
 	# commit and then many seconds of nothing. We want to show
 	# that one commit as soon as possible.
 	#
 	# Since we can receive arbitrary input, there's no optimal
 	# place to flush. Flushing on a blank line is a heuristic that
 	# happens to match git-log output.
 	if (!length) {
 		local $| = 1;
 	}
 }
 
 # Flush any queued hunk (this can happen when there is no trailing context in
 # the final diff of the input).
 show_hunk(\@removed, \@added);
 
 exit 0;
 
 # Ideally we would feed the default as a human-readable color to
 # git-config as the fallback value. But diff-highlight does
 # not otherwise depend on git at all, and there are reports
 # of it being used in other settings. Let's handle our own
 # fallback, which means we will work even if git can't be run.
 sub color_config {
 	my ($key, $default) = @_;
 	my $s = `git config --get-color $key 2>/dev/null`;
 	return length($s) ? $s : $default;
 }
 
 sub show_hunk {
 	my ($a, $b) = @_;
 
 	# If one side is empty, then there is nothing to compare or highlight.
 	if (!@$a || !@$b) {
 		print @$a, @$b;
 		return;
 	}
 
 	# If we have mismatched numbers of lines on each side, we could try to
 	# be clever and match up similar lines. But for now we are simple and
 	# stupid, and only handle multi-line hunks that remove and add the same
 	# number of lines.
 	if (@$a != @$b) {
 		print @$a, @$b;
 		return;
 	}
 
 	my @queue;
 	for (my $i = 0; $i < @$a; $i++) {
 		my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
 		print $rm;
 		push @queue, $add;
 	}
 	print @queue;
 }
 
 sub highlight_pair {
 	my @a = split_line(shift);
 	my @b = split_line(shift);
 
 	# Find common prefix, taking care to skip any ansi
 	# color codes.
 	my $seen_plusminus;
 	my ($pa, $pb) = (0, 0);
 	while ($pa < @a && $pb < @b) {
 		if ($a[$pa] =~ /$COLOR/) {
 			$pa++;
 		}
 		elsif ($b[$pb] =~ /$COLOR/) {
 			$pb++;
 		}
 		elsif ($a[$pa] eq $b[$pb]) {
 			$pa++;
 			$pb++;
 		}
 		elsif (!$seen_plusminus && $a[$pa] eq '-' && $b[$pb] eq '+') {
 			$seen_plusminus = 1;
 			$pa++;
 			$pb++;
 		}
 		else {
 			last;
 		}
 	}
 
 	# Find common suffix, ignoring colors.
 	my ($sa, $sb) = ($#a, $#b);
 	while ($sa >= $pa && $sb >= $pb) {
 		if ($a[$sa] =~ /$COLOR/) {
 			$sa--;
 		}
 		elsif ($b[$sb] =~ /$COLOR/) {
 			$sb--;
 		}
 		elsif ($a[$sa] eq $b[$sb]) {
 			$sa--;
 			$sb--;
 		}
 		else {
 			last;
 		}
 	}
 
 	if (is_pair_interesting(\@a, $pa, $sa, \@b, $pb, $sb)) {
 		return highlight_line(\@a, $pa, $sa, \@OLD_HIGHLIGHT),
 		       highlight_line(\@b, $pb, $sb, \@NEW_HIGHLIGHT);
 	}
 	else {
 		return join('', @a),
 		       join('', @b);
 	}
 }
 
 sub split_line {
 	local $_ = shift;
 	return utf8::decode($_) ?
 		map { utf8::encode($_); $_ }
 			map { /$COLOR/ ? $_ : (split //) }
 			split /($COLOR+)/ :
 		map { /$COLOR/ ? $_ : (split //) }
 		split /($COLOR+)/;
 }
 
 sub highlight_line {
 	my ($line, $prefix, $suffix, $theme) = @_;
 
 	my $start = join('', @{$line}[0..($prefix-1)]);
 	my $mid = join('', @{$line}[$prefix..$suffix]);
 	my $end = join('', @{$line}[($suffix+1)..$#$line]);
 
 	# If we have a "normal" color specified, then take over the whole line.
 	# Otherwise, we try to just manipulate the highlighted bits.
 	if (defined $theme->[0]) {
 		s/$COLOR//g for ($start, $mid, $end);
 		chomp $end;
 		return join('',
 			$theme->[0], $start, $RESET,
 			$theme->[1], $mid, $RESET,
 			$theme->[0], $end, $RESET,
 			"\n"
 		);
 	} else {
 		return join('',
 			$start,
 			$theme->[1], $mid, $theme->[2],
 			$end
 		);
 	}
 }
 
 # Pairs are interesting to highlight only if we are going to end up
 # highlighting a subset (i.e., not the whole line). Otherwise, the highlighting
 # is just useless noise. We can detect this by finding either a matching prefix
 # or suffix (disregarding boring bits like whitespace and colorization).
 sub is_pair_interesting {
 	my ($a, $pa, $sa, $b, $pb, $sb) = @_;
 	my $prefix_a = join('', @$a[0..($pa-1)]);
 	my $prefix_b = join('', @$b[0..($pb-1)]);
 	my $suffix_a = join('', @$a[($sa+1)..$#$a]);
 	my $suffix_b = join('', @$b[($sb+1)..$#$b]);
 
 	return $prefix_a !~ /^$COLOR*-$BORING*$/ ||
 	       $prefix_b !~ /^$COLOR*\+$BORING*$/ ||
 	       $suffix_a !~ /^$BORING*$/ ||
 	       $suffix_b !~ /^$BORING*$/;
 }