The Repo tool manages our local checkouts. See the CrOS Source Layout documentation for much more detailed information about the upstream ChromeOS sources.
See the upstream repo manifest format documentation for general info on manifests and its specification.
$ repo init -b kirkstone -u https://github.com/konsulko/chromeos-yocto-manifest.git
$ repo sync -j4
$ repo forall -pc 'git checkout --track $REPO_REMOTE/$REPO_RREV'
$ source ./meta-chromeos/cros-init-build-env [build-directory]