$ git clone -n https://src.fedoraproject.org/rpms/rust-nix.git /var/lib/mock/f42-build-side-1-3583702-46890/root/chroot_tmpdir/scmroot/rust-nix
Cloning into '/var/lib/mock/f42-build-side-1-3583702-46890/root/chroot_tmpdir/scmroot/rust-nix'...
$ git fetch origin 1fc0c44c393d19f05af88ee6042d30ddf7b743fb:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-nix
 * [new ref]         1fc0c44c393d19f05af88ee6042d30ddf7b743fb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1fc0c44 Update to version 0.30.1; Fixes RHBZ#2362868