$ git clone -n https://src.fedoraproject.org/rpms/R-filehash.git /var/lib/mock/f42-build-side-1-3500769-45971/root/chroot_tmpdir/scmroot/R-filehash
Cloning into '/var/lib/mock/f42-build-side-1-3500769-45971/root/chroot_tmpdir/scmroot/R-filehash'...
$ git fetch origin 932a04a35d95a82e693c6f4a650adb87624291fa:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-filehash
 * [new ref]         932a04a35d95a82e693c6f4a650adb87624291fa -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 932a04a R-maint-sig mass rebuild