[gnulib-tool-py] Dependencies with different conditions

[address@hidden]

Hi Bruno,

I improved the code, though I had to create a new class GLModuleDict. It is
de facto an old dict object, but it makes the work with modules and their
dependencies easy and fast (it takes about 1.5 seconds to process all
conditional dependencies for m4 package). However, there is a situation, which
must be discussed.

To understand what I mean you have to look into stddef and string modules which
you can find in the latest commit (you need files from my git, because they are
a bit modified). You can see that string contains stddef and include_next as
unconditional dependencies. Module stddef contains include_next with condition
[$JUST_TO_TEST_DIFFERENT_SITUATIONS = 1]. What happens next: pygnulib sees that
string has stddef and include_next as dependencies and adds them. When it
processes through stddef, it finds that include_next is a conditional
dependency, so pygnulib add it again if it sees that conditions are different.

The more complicated situation could happen if string had include_next with
condition [test $SITUATION_1 = 1] and stddef had include_next with condition
[test $SITUATION_2].

So, what we must do in such situations? Can such situation ever happen?