$ git clone -n https://src.fedoraproject.org/rpms/nginx.git /var/lib/mock/f41-build-772694-13507/root/chroot_tmpdir/scmroot/nginx
Cloning into '/var/lib/mock/f41-build-772694-13507/root/chroot_tmpdir/scmroot/nginx'...
$ git fetch origin ff3a97eeb5ec50332196a07d06548053e89bff44:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/nginx
 * [new ref]         ff3a97eeb5ec50332196a07d06548053e89bff44 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ff3a97e Increase nginx's epoch to avoid possible regression in CentOS/RHEL (CS-2046)