$ git clone -n https://src.fedoraproject.org/rpms/perl-Chemistry-Isotope.git /var/lib/mock/f45-build-22277-590/root/chroot_tmpdir/scmroot/perl-Chemistry-Isotope
Cloning into '/var/lib/mock/f45-build-22277-590/root/chroot_tmpdir/scmroot/perl-Chemistry-Isotope'...
$ git fetch origin 5c8f0f6f48db34a5fc070e63bc2435e85a01aebf:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Chemistry-Isotope
 * [new ref]         5c8f0f6f48db34a5fc070e63bc2435e85a01aebf -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5c8f0f6 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild