$ git clone -n https://src.fedoraproject.org/rpms/rhythmbox-alternative-toolbar.git /var/lib/mock/f39-build-1764227-41501/root/chroot_tmpdir/scmroot/rhythmbox-alternative-toolbar
Cloning into '/var/lib/mock/f39-build-1764227-41501/root/chroot_tmpdir/scmroot/rhythmbox-alternative-toolbar'...
$ git fetch origin b26edef3a4a7b763f840d20f4eaca75fd0ab9d46:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rhythmbox-alternative-toolbar
 * [new ref]         b26edef3a4a7b763f840d20f4eaca75fd0ab9d46 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b26edef Switch to upstream tarball, use rpmautospec macros