$ git clone -n https://src.fedoraproject.org/rpms/R-DynDoc.git /var/lib/mock/f43-build-58895032-6569073/root/chroot_tmpdir/scmroot/R-DynDoc
Cloning into '/var/lib/mock/f43-build-58895032-6569073/root/chroot_tmpdir/scmroot/R-DynDoc'...
$ git fetch origin 55891d44737473be45011f86a6a19dd41354571d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-DynDoc
 * [new ref]         55891d44737473be45011f86a6a19dd41354571d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 55891d4 R-maint-sig mass rebuild