Include_sections
      module 
       type 
       Something
      
       = sig ... 
       end
      
     
    A module type.
Let's include 
    
     Something
     once
   
foo
Some text.
Let's include 
    
     Something
     a second time: the heading level should be shift here.
   
foo
Some text.
Shifted some more.
foo
Some text.
And let's include it again, but without inlining it this time: the ToC shouldn't grow.