Honor extractor's umask in git-tar-tree.

The archive generated with git-tar-tree had 0755 and 0644 mode bits.
This inconvenienced the extractor with umask 002 by robbing g+w bit
unconditionally.  Just write it out with loose permissions bits and
let the umask of the extractor do its job.

Signed-off-by: Junio C Hamano <redacted>
---
Junio C Hamano [off-list ref] writes:

Unrelated to the topic at hand, but related to the mode bits --
tar-tree generates archives with 0644/0755 permission bits.  It
might not be a bad idea to just let the tar command honor umask
of the extracter, by storing 0666 and 0777 in the archive.

I always work in an environment where umask 002 is the norm, and
get irritated when upstream tarballs of other peoples' projects
create directories with mode 0755, making me do chmod 2775 on
them.

diff --git a/tar-tree.c b/tar-tree.c
--- a/tar-tree.c
+++ b/tar-tree.c

@@ -353,6 +353,7 @@ static void traverse_tree(void *buffer, 
 
 		if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
 			die("corrupt 'tree' file");
+		mode |= (mode & 0100) ? 0777 : 0666;
 		buffer = sha1 + 20;
 		size -= namelen + 20;