$ git clone -n https://src.fedoraproject.org/rpms/bootc.git /var/lib/mock/f39-build-1934990-43119/root/chroot_tmpdir/scmroot/bootc
Cloning into '/var/lib/mock/f39-build-1934990-43119/root/chroot_tmpdir/scmroot/bootc'...
$ git fetch origin eadfb3fbf79e1dd1d2695b01abe857f109a6f6aa:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/bootc
 * [new ref]         eadfb3fbf79e1dd1d2695b01abe857f109a6f6aa -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at eadfb3f local build