add LICENSE file, this is MIT-licensed
git-diff out, git-diff-tree in

the former is porcelain, the latter plumbing; see git(1).
makefile: `all` includes PKGBUILD, $(name).spec
tests/*.t: one test per file

at least until cram learns finer-grained patch application.
(mantle.public / head)-related behavior closer to manpage
config / arguments handled w/o spaghetti

usage message is gone, git-mantle always relays specific messages
(and normalizes error codes) from plumbing.
manpage exact about mantle.upstream

it actually defaults to a bare remote name, not a refspec.
the effective default is thus `upstream/HEAD`, not just `upstream`;
it's definitely not `upstream/master`.
gitglossary(7): it's "remote-tracking branch"
docs: mantle.publicurl doesn't really exist

a leftover from early explorations