$ git clone -n https://src.fedoraproject.org/rpms/rust-regex-syntax.git /var/lib/mock/f41-build-side-1-2993526-36026/root/chroot_tmpdir/scmroot/rust-regex-syntax
Cloning into '/var/lib/mock/f41-build-side-1-2993526-36026/root/chroot_tmpdir/scmroot/rust-regex-syntax'...
$ git fetch origin b15c2bc47e2e9a1045d9bfbb54768250eb618c0e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-regex-syntax
 * [new ref]         b15c2bc47e2e9a1045d9bfbb54768250eb618c0e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b15c2bc Update to version 0.8.5; Fixes RHBZ#2315563