$ git clone -n https://src.fedoraproject.org/rpms/nbdkit.git /var/lib/mock/f40-build-830106-14315/root/chroot_tmpdir/scmroot/nbdkit
Cloning into '/var/lib/mock/f40-build-830106-14315/root/chroot_tmpdir/scmroot/nbdkit'...
$ git fetch origin 6da8d0520f78a92b90e774bedb5c1e5c738ac2ae:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/nbdkit
 * [new ref]         6da8d0520f78a92b90e774bedb5c1e5c738ac2ae -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6da8d05 New stable branch version 1.38.2