$ git clone -n https://src.fedoraproject.org/rpms/R-MatrixGenerics.git /var/lib/mock/f39-build-1524669-36035/root/chroot_tmpdir/scmroot/R-MatrixGenerics
Cloning into '/var/lib/mock/f39-build-1524669-36035/root/chroot_tmpdir/scmroot/R-MatrixGenerics'...
$ git fetch origin 2ca1c580ed2b2b267add0c3c65384700191fe0fd:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-MatrixGenerics
 * [new ref]         2ca1c580ed2b2b267add0c3c65384700191fe0fd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2ca1c58 Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild