t0021/rot13-filter: add packet_initialize()

Let's refactor the code to initialize communication into its own
packet_initialize() function, so that we can reuse this
functionality in following patches.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: chriscool

t/t0021/rot13-filter.pl

@@ -127,19 +127,25 @@ sub packet_flush {
 	STDOUT->flush();
 }
 
+sub packet_initialize {
+	my ($name, $version) = @_;
+
+	packet_compare_lists([0, $name . "-client"], packet_txt_read()) ||
+		die "bad initialize";
+	packet_compare_lists([0, "version=" . $version], packet_txt_read()) ||
+		die "bad version";
+	packet_compare_lists([1, ""], packet_bin_read()) ||
+		die "bad version end";
+
+	packet_txt_write( $name . "-server" );
+	packet_txt_write( "version=" . $version );
+	packet_flush();
+}
+
 print $debug "START\n";
 $debug->flush();
 
-packet_compare_lists([0, "git-filter-client"], packet_txt_read()) ||
-	die "bad initialize";
-packet_compare_lists([0, "version=2"], packet_txt_read()) ||
-	die "bad version";
-packet_compare_lists([1, ""], packet_bin_read()) ||
-	die "bad version end";
-
-packet_txt_write("git-filter-server");
-packet_txt_write("version=2");
-packet_flush();
+packet_initialize("git-filter", 2);
 
 packet_compare_lists([0, "capability=clean"], packet_txt_read()) ||
 	die "bad capability";