$ git clone -n https://src.fedoraproject.org/rpms/rust-crossbeam-epoch.git /var/lib/mock/f39-build-2165740-50984/root/chroot_tmpdir/scmroot/rust-crossbeam-epoch
Cloning into '/var/lib/mock/f39-build-2165740-50984/root/chroot_tmpdir/scmroot/rust-crossbeam-epoch'...
$ git fetch origin 1a9b38fff656813b81216799e4dd522539440aa1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-crossbeam-epoch
 * [new ref]         1a9b38fff656813b81216799e4dd522539440aa1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1a9b38f Update to version 0.9.17; Fixes RHBZ#2254355