$ git clone -n https://src.fedoraproject.org/rpms/rust-trybuild.git /var/lib/mock/f42-build-side-1-3581476-46829/root/chroot_tmpdir/scmroot/rust-trybuild
Cloning into '/var/lib/mock/f42-build-side-1-3581476-46829/root/chroot_tmpdir/scmroot/rust-trybuild'...
$ git fetch origin b96733156fe12756c7e2f3c9965c45d4611a0398:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-trybuild
 * [new ref]         b96733156fe12756c7e2f3c9965c45d4611a0398 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b967331 Update to version 1.0.105; Fixes RHBZ#2365569