`mix deps.update` should propagate dependencies

[josevalim]

If I update dependency :a and :b depends on :a, :b should be recompiled by default (otherwise someone doing a full checkout can get a different result).

[ericmj]

deps.compile should also propagate, right?

This should probably be implemented after caching of dependencies is added. If we could store all dependencies as a tree this issue would be trivial to implement.

[josevalim]

You are right. What I had in mind was simply to store the deps of each project inside Mix.Dep. So after calling Mix.Deps.all, it would be easy to loop recursively checking everyone that depends on X.

If we really want the tree, we could implement it and have it spit out an iterator whenever we want to iterate it. :)

[ericmj]

Ok, the tree can just as well be inline in the current data structure - no need to make an explicit tree.

[josevalim]

That's kind of what we have right now but it would still require you to go through multiple loops in order to get all affected dependencies because the flat structure has no idea of nesting (we just know they are properly ordered).