$ git clone -n https://src.fedoraproject.org/rpms/R-gh /var/lib/mock/f39-build-1596696-38393/root/chroot_tmpdir/scmroot/R-gh
Cloning into '/var/lib/mock/f39-build-1596696-38393/root/chroot_tmpdir/scmroot/R-gh'...
$ git fetch origin 2c26ca7d40f0e11b25c1f07f7874ac47c78e3890:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gh
 * [new ref]         2c26ca7d40f0e11b25c1f07f7874ac47c78e3890 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2c26ca7 Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild