For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mreggie/openSUSE_Tumbleweed/home:mreggie.repo
zypper refresh
zypper install dirdiff
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mreggie/openSUSE_Factory/home:mreggie.repo
zypper refresh
zypper install dirdiff
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mreggie/15.4/home:mreggie.repo
zypper refresh
zypper install dirdiff