tar on Mac does not like empty tar from git archive

Git 1.8.2.1 includes commit bd54cf17 - archive: handle commits with an empty tree

Test 2 of t5004-archive-corner-cases, "tar archive of empty tree is empty", fails on Mac OS X 10.8.3 (with XCode 4.6.1) since the tar command exits with return code 1 on the generated  tar file.

expecting success: 
	git archive --format=tar HEAD >empty.tar &&
	make_dir extract &&
	"$TAR" xf empty.tar -C extract &&
	check_dir extract

tar: Damaged tar archive tar: Error exit delayed from previous errors. not ok 2 - tar archive of empty tree is empty

tar tf "trash directory.t5004-archive-corner-cases/empty.tar"; echo $? tar: Damaged tar archive tar: Error exit delayed from previous errors. 1

tar --version bsdtar 2.8.3 - libarchive 2.8.3

It appears that bsdtar does not like the empty tar files created by git archive. An empty tar file created by bsdtar is accepted.

tar cT /dev/null | tar t; echo $? 0

On Mon, Apr 08, 2013 at 02:36:05PM -0400, BJ Hargrave wrote:

Hmm. So I guess the question is: do we need to work around this in the test for platforms that do not like empty tar files, or are the empty tarfiles we are making wrong somehow?

That makes me think the latter ("we are wrong"). I don't have my OS X box handy; can you provide a sample empty tarfile that it creates?

-Peff

On Apr 8, 2013, at 17:05 , Jeff King <peff@peff.net> wrote:

I created mac.tar on my Mac and linux.tar on a RHEL6.3 machine (tar (GNU tar) 1.23). Both were created with 

tar cTf /dev/null xxx.tar

Both files are accepted by tar on both the Mac and the RHEL machines. (Both files contain nothing but zeros.)

Am 08.04.2013 23:05, schrieb Jeff King:

libarchive (on which bsdtar is based) doesn't like extended pax headers at the end of archives. Here's the relevant source file:

https://github.com/libarchive/libarchive/blob/master/libarchive/archive_read_support_format_tar.c

tar_read_header() calls header_pax_global() to handle a global pax header, which in turn calls tar_read_header() again to fetch the next header. If it reaches the end of the archive then err is set to ARCHIVE_EOF and "Damaged tar archive" is reported at the end of this function.

I tried come up with a small patch that convinces it to ignore such a condition, but it's apparently not as easy as it looks -- I just made bsdtar report even more obscure errors. Will look deeper into it later this week.

René

Am 08.04.2013 20:36, schrieb BJ Hargrave:

I've opened an issue for libarchive for that behaviour: http://code.google.com/p/libarchive/issues/detail?id=314

We can work around bsdtar's dislike of not-quite-empty tar archives by leaving out the comment that contains the commit hash.

-- >8 --
Subject: t5004: fix issue with empty archive test and bsdtar

bsdtar, which is the default tar on Mac OS X, handles empty archives just fine but reports archives containing only a pax extended header comment as damaged. Work around the issue by explicitly generating the archive for the tree and not the commit, which causes git archive to omit the commit hash comment record from the tar file.

Reported-by: BJ Hargrave <bj@bjhargrave.com>
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
---
 t/t5004-archive-corner-cases.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)