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|
#!/usr/bin/perl
# Highlight by reversing foreground and background. You could do
# other things like bold or underline if you prefer.
my $HIGHLIGHT = "\x1b[7m";
my $UNHIGHLIGHT = "\x1b[27m";
my $COLOR = qr/\x1b\[[0-9;]*m/;
my @window;
while (<>) {
# We highlight only single-line changes, so we need
# a 4-line window to make a decision on whether
# to highlight.
push @window, $_;
next if @window < 4;
if ($window[0] =~ /^$COLOR*(\@| )/ &&
$window[1] =~ /^$COLOR*-/ &&
$window[2] =~ /^$COLOR*\+/ &&
$window[3] !~ /^$COLOR*\+/) {
print shift @window;
show_pair(shift @window, shift @window);
}
else {
print shift @window;
}
# 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;
}
}
# Special case a single-line hunk at the end of file.
if (@window == 3 &&
$window[0] =~ /^$COLOR*(\@| )/ &&
$window[1] =~ /^$COLOR*-/ &&
$window[2] =~ /^$COLOR*\+/) {
print shift @window;
show_pair(shift @window, shift @window);
}
# And then flush any remaining lines.
while (@window) {
print shift @window;
}
exit 0;
sub show_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;
}
}
print highlight(\@a, $pa, $sa);
print highlight(\@b, $pb, $sb);
}
sub split_line {
local $_ = shift;
return map { /$COLOR/ ? $_ : (split //) }
split /($COLOR*)/;
}
sub highlight {
my ($line, $prefix, $suffix) = @_;
return join('',
@{$line}[0..($prefix-1)],
$HIGHLIGHT,
@{$line}[$prefix..$suffix],
$UNHIGHLIGHT,
@{$line}[($suffix+1)..$#$line]
);
}
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