$ git clone -n https://src.fedoraproject.org/rpms/rust-serde_with.git /var/lib/mock/f40-build-2101694-50515/root/chroot_tmpdir/scmroot/rust-serde_with
Cloning into '/var/lib/mock/f40-build-2101694-50515/root/chroot_tmpdir/scmroot/rust-serde_with'...
$ git fetch origin c131a3b9e60e0fa51473f0521ab1e848591da1af:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-serde_with
 * [new ref]         c131a3b9e60e0fa51473f0521ab1e848591da1af -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c131a3b Update to version 3.4.0; Fixes RHBZ#2073002