$ git clone -n https://src.fedoraproject.org/rpms/rust-cxx.git /var/lib/mock/f39-build-1526230-36059/root/chroot_tmpdir/scmroot/rust-cxx
Cloning into '/var/lib/mock/f39-build-1526230-36059/root/chroot_tmpdir/scmroot/rust-cxx'...
$ git fetch origin 98e753231f79c737acd864b2ed97f830f76e1134:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cxx
 * [new ref]         98e753231f79c737acd864b2ed97f830f76e1134 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 98e7532 update to version 1.0.110 (rhbz#2246683)