add -i: add function to format hunk header

This code is duplicated in a couple of places so make it into a
function as we're going to add some more callers shortly.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: phillipwood

git-add--interactive.perl

@@ -751,6 +751,15 @@ sub parse_hunk_header {
 	return ($o_ofs, $o_cnt, $n_ofs, $n_cnt);
 }
 
+sub format_hunk_header {
+	my ($o_ofs, $o_cnt, $n_ofs, $n_cnt) = @_;
+	return ("@@ -$o_ofs" .
+		(($o_cnt != 1) ? ",$o_cnt" : '') .
+		" +$n_ofs" .
+		(($n_cnt != 1) ? ",$n_cnt" : '') .
+		" @@\n");
+}
+
 sub split_hunk {
 	my ($text, $display) = @_;
 	my @split = ();
@@ -838,11 +847,7 @@ sub split_hunk {
 		my $o_cnt = $hunk->{OCNT};
 		my $n_cnt = $hunk->{NCNT};
 
-		my $head = ("@@ -$o_ofs" .
-			    (($o_cnt != 1) ? ",$o_cnt" : '') .
-			    " +$n_ofs" .
-			    (($n_cnt != 1) ? ",$n_cnt" : '') .
-			    " @@\n");
+		my $head = format_hunk_header($o_ofs, $o_cnt, $n_ofs, $n_cnt);
 		my $display_head = $head;
 		unshift @{$hunk->{TEXT}}, $head;
 		if ($diff_use_color) {
@@ -912,11 +917,7 @@ sub merge_hunk {
 		}
 		push @line, $line;
 	}
-	my $head = ("@@ -$o0_ofs" .
-		    (($o_cnt != 1) ? ",$o_cnt" : '') .
-		    " +$n0_ofs" .
-		    (($n_cnt != 1) ? ",$n_cnt" : '') .
-		    " @@\n");
+	my $head = format_hunk_header($o0_ofs, $o_cnt, $n0_ofs, $n_cnt);
 	@{$prev->{TEXT}} = ($head, @line);
 }