This change allows developers to easily create a sanitized source
archive for example:
git archive --format=tar --prefix=wsjtx-2.0.0/ wsjtx-2.0.0-rc1 | gzip >wsjtx-2.0.0-rc1.tgz
Which creates a sources tarball called wsjtx-2.0.0-rc1.tgz from the
wsjtx-2.0.0-rc1 tag (substitute HEAD or a branch name or even a commit
SHA for other contents).