[pca] Wrong patches downloaded

[Martin Paul]

Don,

Thanks a lot for the detailed explanation and background information!

That's something I can quote in the future. Maybe you could ask Gerry to 
publish it in his patch blog as well.

> Patches such as these will typically contain code in the patch's prepatch
 > script in order to prevent the patches being applied on top of the 
wrong OS.

And this is exactly what I usually duplicate in pca's set_extra_req() 
and chk_extra_req() functions to fix such issues.

In a perfect world, there would be a formal language to desribe such 
extra requirements which would be included in patchdiag.xref. Then one 
source could be used both by a patch analysis tool and by patchadd, 
turning this into a non-issue.

I understand that this was a reason for smpatch's "realizations", but 
the concept wasn't taken far enough and/or the implementation was 
suboptimal.

Martin.