Gentoo - build your own ebuild manual

Manuals at planet gentoo

Gentoo Development Guide
Ebuild HOWTO
Eclass HOWTO

cheap tricks

to omit a compile (distutils.eclass):

src_compile() { :; }

downloading a special-tag from github:

EAPI="3"

GITHUB_USER="mig"
GITHUB_TAG="${PV}"
HOMEPAGE="https://github.com/${GITHUB_USER}/${PN}"
SRC_URI="https://github.com/${GITHUB_USER}/${PN}/tarball/${GITHUB_TAG} -> ${GITHUB_USER}-${P}.tar.gz"
S="${WORKDIR}/${GITHUB_USER}-${PN}-${GITHUB_TAG}"