contrib/diffall: eliminate use of tar

The 'tar' utility is not available on all platforms (some only support
'gnutar').  An earlier commit created a work-around for this problem,
but a better solution is to eliminate the use of 'tar' completely.

Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/diffall/git-diffall

@@ -202,10 +202,14 @@ then
 		fi
 	done < "$tmp/filelist"
 else
-	# Mac users have gnutar rather than tar
-	(tar --ignore-failed-read -c -T "$tmp/filelist" | (cd "$tmp/$right_dir" && tar -x)) || {
-		gnutar --ignore-failed-read -c -T "$tmp/filelist" | (cd "$tmp/$right_dir" && gnutar -x)
-	}
+	while read name
+	do
+		if test -e "$name"
+		then
+			mkdir -p "$tmp/$right_dir/$(dirname "$name")"
+			cp "$name" "$tmp/$right_dir/$name"
+		fi
+	done < "$tmp/filelist"
 fi
 
 # Populate the tmp/left_dir directory with the files to be compared