$ git clone -n https://src.fedoraproject.org/rpms/R-devtools.git /var/lib/mock/f40-build-1930472-25111/root/chroot_tmpdir/scmroot/R-devtools
Cloning into '/var/lib/mock/f40-build-1930472-25111/root/chroot_tmpdir/scmroot/R-devtools'...
$ git fetch origin d894751cfb20937d2ee098e0cb4078fcb419550f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-devtools
 * [new ref]         d894751cfb20937d2ee098e0cb4078fcb419550f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d894751 R-maint-sig mass rebuild