$ git clone -n https://src.fedoraproject.org/rpms/rust-syn.git /var/lib/mock/f40-build-2271436-54887/root/chroot_tmpdir/scmroot/rust-syn
Cloning into '/var/lib/mock/f40-build-2271436-54887/root/chroot_tmpdir/scmroot/rust-syn'...
$ git fetch origin b0d8e5681c760cfc7095e90c440174da4516d92c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-syn
 * [new ref]         b0d8e5681c760cfc7095e90c440174da4516d92c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b0d8e56 Update to version 2.0.48; Fixes RHBZ#2256697