Install headers into manifold subdirectory

[cjmayo]

Basically this goes back to the way things were. I think it addresses #701 OK, don't know if there are other ideas.

/usr/include/manifold/meshIO.h
/usr/include/manifold/sdf.h
/usr/include/manifold/manifold.h
/usr/include/manifold/polygon.h
/usr/include/manifold/cross_section.h
/usr/include/manifold/collider.h
/usr/include/manifold/vec_view.h
/usr/include/manifold/public.h

Because of the CMake config files I am able to build OpenSCAD (modified to use find_package(manifold)) with either master or this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3b8282e) 91.67% compared to head (7d01878) 91.67%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #729   +/-   ##
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  Coverage   91.67%   91.67%           
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  Files          37       37           
  Lines        4732     4732           
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  Hits         4338     4338           
  Misses        394      394           

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[elalish]

Thanks, sounds good to me, but I don't understand library installs well enough to review this with any confidence. If @pca006132 is happy and it works for OpenSCAD, then I'm happy.

[pca006132]

Looks fine to me, but ultimately I think we should change headers such as public.h to something else, or it will conflict with others...

[elalish]

Can you help me understand this better? I think what's happening here is that instead of installing usr/include/public.h, which might collide with anything called public.h, we're installing usr/include/manifold/public.h, which shouldn't collide with anything except maybe another library called manifold. Or am I misunderstanding how header conflicts happen?

[pca006132]

Yeah this avoids conflict during installation, but if a user uses two packages with public.h, the include will have conflict as well.

[elalish]

Oh, I thought you'd still have to put #include <manifold/public.h>.

[pca006132]

That requires changing our current directory structure and includes.