class Bootsnap::LoadPathCache::Cache

is true.
e.g. given "/a/b/c/d" exists, and the path is ["/a/b"], has_dir?("c/d")
Does this directory exist as a child of one of the path items?

def has_dir?(dir)
  reinitialize if stale?
  @mutex.synchronize { @dirs[dir] }
end