Previously, superenv did not try to filter -I or -L flags
based on the list of requested dependencies; as a result, buildsystems
which opportunistically discover Homebrew-installed libraries were able
to link against them even under superenv.
This adds a list of all requested dependencies to the superenv environment,
and compares all -I and -L flags against those; any Cellar and opt paths
found which resolve to unrequested dependencies are filtered out.
This is the (partially) documented public API for Homebrew.
The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.
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