I support this proposal, as someone who no longer releases tarballs
of my software, when I can possibly avoid it. I have worried about
signed tags / commits only being a SHA1 break away from useless.

As to the implementation, checksumming the collection of raw objects is
certainly superior to tar. Colin had suggested sorting the objects by
checksum, but I don't think that is necessary. Just stream the commit
object, then its tree object, followed by the content of each object
listed in the tree, recursing into subtrees as necessary. That will be a
stable stream for a given commit, or tree.

-- 
see shy jo