import-tars: Use the "Link indicator" to identify directories

Earlier, we used the mode to determine if a name was associated with
a directory. This fails, since some tar programs do not set the mode
correctly. However, the link indicator _has_ to be set correctly.

Noticed by Chris Riddoch.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Acked-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

contrib/fast-import/import-tars.perl

@@ -75,7 +75,7 @@
 		$mode = oct $mode;
 		$size = oct $size;
 		$mtime = oct $mtime;
-		next if $mode & 0040000;
+		next if $typeflag == 5; # directory
 
 		print FI "blob\n", "mark :$next_mark\n", "data $size\n";
 		while ($size > 0 && read(I, $_, 512) == 512) {