print options conflicts

[memsharded]

Changelog: Feature: Print options conflicts in the graph caused by different branches recipes defining options values.
Docs: conan-io/docs#3643

Close #15865

[zhanglin-zhou]

Thanks very much for your fix, @memsharded. Based on testing for the simple recipe in issue #15865:

1. When I change the order of zlib and libpng in recipe, then no warning. Do you think we still need to output conflict options here? Because conflict still happen.
2. zlib/1.3:shared=False (current value) is it possible to output like zlib/1.3:shared=False (current value from libpng/1.6.43)? So that people can know when it comes from.

I will integrate your patch to our product, which is complex project to see what happen.

[memsharded]

When I change the order of zlib and libpng in recipe, then no warning. Do you think we still need to output conflict options here? Because conflict still happen.

Not really,libpng is not defining options values for zlib. The detection only checks the options explicitly set in recipes. If they succeed in setting the value, and there is no other recipe trying to do the same and conflicting, it is not necessary to report it.

zlib/1.3:shared=False (current value) is it possible to output like zlib/1.3:shared=False (current value from libpng/1.6.43)? So that people can know when it comes from.

I am afraid that would be a bit too costly. At the moment, only when a diamond in the graph is being closed this is triggered, but to be able to print this, it would be necessary to store that information for every graph requirement expansion.