$ git clone -n https://src.fedoraproject.org/rpms/rust.git /var/lib/mock/f42-build-side-1-3582314-46884/root/chroot_tmpdir/scmroot/rust
Cloning into '/var/lib/mock/f42-build-side-1-3582314-46884/root/chroot_tmpdir/scmroot/rust'...
$ git fetch origin 17cb547e45d2d49ce6fe61225354b927da6a3d1d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust
 * [new ref]         17cb547e45d2d49ce6fe61225354b927da6a3d1d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 17cb547 Update to Rust 1.88.0