$ git clone -n https://src.fedoraproject.org/rpms/rust-libcst.git /var/lib/mock/f40-build-1430274-23572/root/chroot_tmpdir/scmroot/rust-libcst
Cloning into '/var/lib/mock/f40-build-1430274-23572/root/chroot_tmpdir/scmroot/rust-libcst'...
$ git fetch origin e3a6a0d8f14798fbe6ee19946ed9e96a27bd70a3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-libcst
 * [new ref]         e3a6a0d8f14798fbe6ee19946ed9e96a27bd70a3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e3a6a0d Update to version 1.4.0; Fixes RHBZ#2282550