$ git clone -n https://src.fedoraproject.org/rpms/rust-libc.git /var/lib/mock/f45-build-42908-797/root/chroot_tmpdir/scmroot/rust-libc
Cloning into '/var/lib/mock/f45-build-42908-797/root/chroot_tmpdir/scmroot/rust-libc'...
$ git fetch origin a1f3270f4f2a755f2a63d9aad2c9a72fe4de5d6d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-libc
 * [new ref]         a1f3270f4f2a755f2a63d9aad2c9a72fe4de5d6d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a1f3270 Update to version 0.2.189; Fixes RHBZ#2503110