$ git clone -n https://src.fedoraproject.org/rpms/rust-syn0.15.git /var/lib/mock/f41-build-side-1-3134946-39764/root/chroot_tmpdir/scmroot/rust-syn0.15
Cloning into '/var/lib/mock/f41-build-side-1-3134946-39764/root/chroot_tmpdir/scmroot/rust-syn0.15'...
$ git fetch origin 73c4d6f2bc30f9489f6a05266578bfb762ec0eaf:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-syn0.15
 * [new ref]         73c4d6f2bc30f9489f6a05266578bfb762ec0eaf -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 73c4d6f compat package no longer needed