Fix infinite loop on mixin self-includes

[Skipants]

Adds ae37c48:

Fixes a regression in 5.0.2 where a module that had code including itself in a class method would cause Brakeman::Tracker#find_method to infinite loop.

Hi! Thanks for the gem! While upgrading from 5.0.1 to 5.0.2 we had this regression when running brakeman in our CI. I narrowed it down to this unorthodox-but-technically-valid-ruby. We have a module in our codebase that includes itself when building a generic class. It caused brakeman to infinite loop on Brakeman::Tracker#find_method. I turned the smallest PoC I could into a test case.

Another way to solve this might be to prevent a class being added to its own includes collection, but this was the easier fix. Thanks, again!

[presidentbeef]

There shouldn't be any regression between 5.0.1->5.0.2. 🤔 Can you try 5.0.4?

[presidentbeef]

Oh. Yeah I messed up 5.0.2. You can use 5.0.4 for now and I'll take a look at this code change.

[presidentbeef]

Hi @Skipants - thanks for the PR.

I think this should be more general. There are a couple other examples of avoiding infinite recursion loops in Brakeman, for example

brakeman/lib/brakeman/tracker/collection.rb

Lines 24 to 34 in 9f2e4b4

	def ancestor? parent, seen={}
	seen[self.name] = true
	if self.parent == parent or seen[self.parent]
	true
	elsif parent_model = collection[self.parent]
	parent_model.ancestor? parent, seen
	else
	false
	end
	end

Can you update this PR to use that approach? Thanks!

[Skipants]

@presidentbeef I updated and rebased based on your suggestion. I think this is what you meant but let me know. I had to add the condition that a class is its own ancestor because that was the case I ran into. I hope that's not too heavy-handed of a change. All the tests pass for me locally.

[presidentbeef]

Thanks!