The .gitattributes, .gitignore, .commit-template files do not need to be
present in packaged sources, as they are for people using the Git
repository. People who download tarballs usually don't reimport into
Git -- they should just download the actual repositories.
Meanwhile, the .tag file is quite useful. Instead of making Git extract
to the useless SHA-1 of the "$Id$\n" string, ask git-archive to store
the SHA-1 of the commit being packaged.
Reviewed-by: Oswald Buddenhagen <firstname.lastname@example.org>