$ git clone -n https://src.fedoraproject.org/rpms/plasma-oxygen.git /var/lib/mock/f41-build-824412-154063/root/chroot_tmpdir/scmroot/plasma-oxygen
Cloning into '/var/lib/mock/f41-build-824412-154063/root/chroot_tmpdir/scmroot/plasma-oxygen'...
$ git fetch origin e21bb5bfd32c92c95d2c0e87b8d4a43b16362f53:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-oxygen
 * [new ref]         e21bb5bfd32c92c95d2c0e87b8d4a43b16362f53 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e21bb5b rebuild