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authorLibravatar René Scharfe <rene.scharfe@lsrfire.ath.cx>2013-05-09 15:13:47 +0200
committerLibravatar Junio C Hamano <gitster@pobox.com>2013-05-09 12:41:31 -0700
commitea2d20d4c2216faa8ff4525e9e73b26509405766 (patch)
tree7e8d22850da6d21dcbb6e2d836334c464784d69d /Documentation/git-cvsimport.txt
parentt5004: ignore pax global header file (diff)
downloadtgif-ea2d20d4c2216faa8ff4525e9e73b26509405766.tar.xz
t5004: avoid using tar for checking emptiness of archive
Test 2 of t5004 checks if a supposedly empty tar archive really contains no files. 24676f02 (t5004: fix issue with empty archive test and bsdtar) removed our commit hash to make it work with bsdtar, but the test still fails on NetBSD and OpenBSD, which use their own tar that considers a tar file containing only NULs as broken. Here's what the different archivers do when asked to create a tar file without entries: $ uname -v NetBSD 6.0.1 (GENERIC) $ gtar --version | head -1 tar (GNU tar) 1.26 $ bsdtar --version bsdtar 2.8.4 - libarchive 2.8.4 $ : >zero.tar $ perl -e 'print "\0" x 10240' >tenk.tar $ sha1 zero.tar tenk.tar SHA1 (zero.tar) = da39a3ee5e6b4b0d3255bfef95601890afd80709 SHA1 (tenk.tar) = 34e163be8e43c5631d8b92e9c43ab0bf0fa62b9c $ : | tar cf - -T - | sha1 da39a3ee5e6b4b0d3255bfef95601890afd80709 $ : | gtar cf - -T - | sha1 34e163be8e43c5631d8b92e9c43ab0bf0fa62b9c $ : | bsdtar cf - -T - | sha1 34e163be8e43c5631d8b92e9c43ab0bf0fa62b9c So NetBSD's native tar creates an empty file, while GNU tar and bsdtar both give us 10KB of NULs -- just like git archive with an empty tree. Now let's see how the archivers handle these two kinds of empty tar files: $ tar tf zero.tar; echo $? tar: Unexpected EOF on archive file 1 $ gtar tf zero.tar; echo $? gtar: This does not look like a tar archive gtar: Exiting with failure status due to previous errors 2 $ bsdtar tf zero.tar; echo $? 0 $ tar tf tenk.tar; echo $? tar: Cannot identify format. Searching... tar: End of archive volume 1 reached tar: Sorry, unable to determine archive format. 1 $ gtar tf tenk.tar; echo $? 0 $ bsdtar tf tenk.tar; echo $? 0 NetBSD's tar complains about both, bsdtar happily accepts any of them and GNU tar doesn't like zero-length archive files. So the safest course of action is to stay with our block-of-NULs format which is compatible with GNU tar and bsdtar, as we can't make NetBSD's native tar happy anyway. We can simplify our test, however, by taking tar out of the picture. Instead of extracting the archive and checking for the non-presence of files, check if the file has a size of 10KB and contains only NULs. This makes t5004 pass on NetBSD and OpenBSD. Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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