$ git clone -n https://src.fedoraproject.org/rpms/libxml++40.git /var/lib/mock/f45-build-17338-498/root/chroot_tmpdir/scmroot/libxml++40
Cloning into '/var/lib/mock/f45-build-17338-498/root/chroot_tmpdir/scmroot/libxml++40'...
$ git fetch origin d90c0cfcf44884b8283321723752f3fa59cb98a9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libxml++40
 * [new ref]         d90c0cfcf44884b8283321723752f3fa59cb98a9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d90c0cf Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild