use parse_hunk_header from git

Author: paulirish

libs/header_clean/header_clean.pl

@@ -59,22 +59,21 @@
 	########################################
 	# Check for "@@ -3,41 +3,63 @@" syntax #
 	########################################
-	} elsif ($change_hunk_indicators && $line =~ /^${ansi_sequence_regex}@@@* (.+?) @@@*(.*)/) {
-		my $file_str     = $4;
+	} elsif ($change_hunk_indicators && $line =~ /^${ansi_sequence_regex}(@@@* .+? @@@*)(.*)/) {
+
+		my $hunk_header  = $4;
 		my $remain       = $5;
 
 		if ($1) {
 			print $1; # Print out whatever color we're using
 		}
 
-		my ($start_line) = $file_str =~ m/\+(\d+)/;
-		$start_line      = abs($start_line + 0);
-
+		my ($orig_offset, $orig_count, $new_offset, $new_count) = parse_hunk_header($hunk_header);
 		$last_file_seen = basename($last_file_seen);
 
 		# Plus three line for context
-		print "@ $last_file_seen:" . ($start_line + 3) . " \@${remain}\n";
-		#print $line;
+		print "@ $last_file_seen:" . ($new_offset + 3) . " \@${remain}\n";
+
 	###################################
 	# Remove any new file permissions #
 	###################################
@@ -105,6 +104,16 @@
 	}
 }
 
+# Courtesy of github.com/git/git/blob/ab5d01a/git-add--interactive.perl#L798-L805
+sub parse_hunk_header {
+    my ($line) = @_;
+    my ($o_ofs, $o_cnt, $n_ofs, $n_cnt) =
+        $line =~ /^@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@/;
+    $o_cnt = 1 unless defined $o_cnt;
+    $n_cnt = 1 unless defined $n_cnt;
+    return ($o_ofs, $o_cnt, $n_ofs, $n_cnt);
+}
+
 sub strip_empty_first_line {
 	my $foo = shift(); # Array passed in by reference