* jd/subtree:
contrib/subtree: allow adding an annotated tag
contrib/subtree/Makefile: clean up rule for "clean"
contrib/subtree/Makefile: clean up rules to generate documentation
contrib/subtree/Makefile: s/libexecdir/gitexecdir/
contrib/subtree/Makefile: use GIT-VERSION-FILE
contrib/subtree/Makefile: scrap unused $(gitdir)