$ git clone -n https://src.fedoraproject.org/rpms/R-magick.git /var/lib/mock/f42-build-side-1-3586719-46924/root/chroot_tmpdir/scmroot/R-magick
Cloning into '/var/lib/mock/f42-build-side-1-3586719-46924/root/chroot_tmpdir/scmroot/R-magick'...
$ git fetch origin 8e792dcb702d7b83e6e5cac8faeab612016f3c96:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-magick
 * [new ref]         8e792dcb702d7b83e6e5cac8faeab612016f3c96 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8e792dc R-maint-sig mass rebuild