$ git clone -n https://src.fedoraproject.org/rpms/rust-bincode.git /var/lib/mock/f42-build-side-1-3589008-46952/root/chroot_tmpdir/scmroot/rust-bincode
Cloning into '/var/lib/mock/f42-build-side-1-3589008-46952/root/chroot_tmpdir/scmroot/rust-bincode'...
$ git fetch origin 3a99757874485ca19bbc68c62c0ac0c1614f9d4a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-bincode
 * [new ref]         3a99757874485ca19bbc68c62c0ac0c1614f9d4a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3a99757 Update to version 2.0.1; Fixes RHBZ#2350432