[PATCH] diff-highlight: Work for multiline changes too

["Michał Kiedrowicz" <michal.kiedrowicz@gmail.com>]

Signed-off-by: Michał Kiedrowicz <michal.kiedrowicz@gmail.com>
---

After looking at outputs I noticed that it can also ignore lines with
prefixes/suffixes that consist only of punctuation (asterisk, semicolon, dot,
etc), because otherwise whole line is highlighted except for terminating
punctuation.

 contrib/diff-highlight/diff-highlight |   96 ++++++++++++++++++++++-----------
 1 files changed, 65 insertions(+), 31 deletions(-)

diff --git a/contrib/diff-highlight/diff-highlight b/contrib/diff-highlight/diff-highlight
index d893898..4811550 100755
--- a/contrib/diff-highlight/diff-highlight
+++ b/contrib/diff-highlight/diff-highlight
@@ -1,28 +1,40 @@
 #!/usr/bin/perl
 
+use warnings;
+use strict;
+
 # 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;
+my $context;
+my @removed = ();
+my @added = ();
+my $started = 0;
 
 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;
+	if (/^$COLOR*-/) {
+		push @removed, $_;
+	} elsif (/^$COLOR*\+/) {
+		push @added, $_;
+	} else {
+		if ($started == 1 ) {
+			show_pairs(\@removed, \@added);
+		} else {
+			print @removed;
+			print @added;
+		}
+		@removed = ();
+		@added = ();
+		print $_;
+
+		if (/^$COLOR*(\@| )/) {
+			$started = 1;
+		} else {
+			$started = 0;
+		}
 	}
 
 	# Most of the time there is enough output to keep things streaming,
@@ -38,23 +50,33 @@ while (<>) {
 	}
 }
 
-# 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;
-}
+show_pairs(\@removed, \@added);
 
 exit 0;
 
-sub show_pair {
+sub show_pairs {
+	my $a = shift;
+	my $b = shift;
+
+	if (scalar(@{$a}) == scalar(@{$b}) && scalar(@${a}) > 0) {
+		my @removed;
+		my @added;
+
+		for(my $i = 0; $i < scalar(@{$a}); $i++) {
+			my ($rm, $add) = highlight_pair($a->[$i], $b->[$i]);
+			push @removed, $rm;
+			push @added, $add;
+		}
+
+		print @removed;
+		print @added;
+	} else {
+		print @{$a};
+		print @{$b};
+	}
+}
+
+sub highlight_pair {
 	my @a = split_line(shift);
 	my @b = split_line(shift);
 
@@ -101,8 +123,20 @@ sub show_pair {
 		}
 	}
 
-	print highlight(\@a, $pa, $sa);
-	print highlight(\@b, $pb, $sb);
+	my $prefa = join('', @a[0..($pa-1)]);
+	my $prefb = join('', @b[0..($pb-1)]);
+	my $sufa = join('', @a[($sa+1)..$#a]);
+	my $sufb = join('', @b[($sb+1)..$#b]);
+
+	# Highlight only if prefix or suffix is interesting (i.e. not consisting
+	# of color and (for prefix) +/-). Otherwise we would highlight whole
+	# lines.
+	if ($prefa =~ /^($COLOR)*-(\s|$COLOR)*$/ && $sufa =~ /^(\s|$COLOR)*$/
+		&& $prefb =~ /^($COLOR)*\+(\s|$COLOR)*$/ && $sufb =~ /^(\s|$COLOR)*$/) {
+		return join('', @a), join('', @b);
+	} else {
+		return highlight(\@a, $pa, $sa), highlight(\@b, $pb, $sb);
+	}
 }
 
 sub split_line {
-- 
1.7.3.4