Make the rest of commands work from a subdirectory.

These commands are converted to run from a subdirectory.

    commit-tree convert-objects merge-base merge-index mktag
    pack-objects pack-redundant prune-packed read-tree tar-tree
    unpack-file unpack-objects update-server-info write-tree

Signed-off-by: Junio C Hamano <junkio@cox.net>

tar-tree.c

@@ -407,6 +407,8 @@ int main(int argc, char **argv)
 	void *buffer;
 	unsigned long size;
 
+	setup_git_directory();
+
 	switch (argc) {
 	case 3:
 		basedir = argv[2];