Comment # 3 on bug 1172891 from Cor Blom

The way I use it can be seen in the package "lyx", which I maintain in
Publishing. In my home repo (home:cornelisbb) I have a link to this package
with a patch containing some personal adaptations that suit me but are not
suited to include in an official package or upstream. I have set it up, using
the option descrbied in the "_link" file that I only need to update the patch
and nothing in the rest of the package. The spec remains the same and the build
service is updating the spec file, including the patch. This does not work with
%autopatch or %autosetup. I had a SR that changed the spec to use %autosetup,
which I reverted, because I like the ease of having that adapted package in my
home repo.

I don't know if this is the intended use, but this is how I use it. And with
%autopatch my added patch is applied twice.