$ git clone -n https://src.fedoraproject.org/rpms/rust-cargo.git /var/lib/mock/f42-build-side-1-3514846-46092/root/chroot_tmpdir/scmroot/rust-cargo
Cloning into '/var/lib/mock/f42-build-side-1-3514846-46092/root/chroot_tmpdir/scmroot/rust-cargo'...
$ git fetch origin 0da05a42a6ec8c421517b8a5cf2a4ca37d040b7d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cargo
 * [new ref]         0da05a42a6ec8c421517b8a5cf2a4ca37d040b7d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0da05a4 Update to version 0.86.0; Fixes RHBZ#2292641