$ git clone -n https://src.fedoraproject.org/rpms/rust-cxx-build.git /var/lib/mock/f39-build-2222992-52713/root/chroot_tmpdir/scmroot/rust-cxx-build
Cloning into '/var/lib/mock/f39-build-2222992-52713/root/chroot_tmpdir/scmroot/rust-cxx-build'...
$ git fetch origin 19e02ca4edcaf7fe01d07af55af4a5312886406b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cxx-build
 * [new ref]         19e02ca4edcaf7fe01d07af55af4a5312886406b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 19e02ca Update to version 1.0.115 (rhbz#2257017)