Re: tar on Mac does not like empty tar from git archive

Am 08.04.2013 23:05, schrieb Jeff King:

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

quoted

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.

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?

quoted

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

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?

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