$ git clone -n https://src.fedoraproject.org/rpms/rust-syn.git /var/lib/mock/f45-build-45309-822/root/chroot_tmpdir/scmroot/rust-syn
Cloning into '/var/lib/mock/f45-build-45309-822/root/chroot_tmpdir/scmroot/rust-syn'...
$ git fetch origin 9f9a13e3c54f1b33316c9a228b897c80ea5cb5a6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-syn
 * [new ref]         9f9a13e3c54f1b33316c9a228b897c80ea5cb5a6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9f9a13e Update to version 3.0.4; Fixes RHBZ#2521702