0c20554f69
As pointed out in #1459, docker cli fails to detect that the input is a tarball, in case it is generated by `git archive --format=tgz`. This happens because `git archive` adds some metadata to the initial tar header, and so it is more than 1 block (of 512 bytes) long, while we only provide 1 block to archive/tar.Next() and it fails. To fix, give it 2 blocks :) Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>