$ git clone -n https://src.fedoraproject.org/rpms/rust-slab.git /var/lib/mock/f39-build-1517181-35696/root/chroot_tmpdir/scmroot/rust-slab
Cloning into '/var/lib/mock/f39-build-1517181-35696/root/chroot_tmpdir/scmroot/rust-slab'...
$ git fetch origin 1dcee59dc12ef3dfef7111361f3c9b8461a50c19:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-slab
 * [new ref]         1dcee59dc12ef3dfef7111361f3c9b8461a50c19 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1dcee59 Update to version 0.4.9; Fixes RHBZ#2233580