-; Return the "depends choice" of autmatically dependent package
-; considering the options of providing that package as currently
-; installed. Only the first of providers is an automatic dependency.
-; Thus, return a) the depedent package itself if it's the first of its
-; providers, or b) that first of providers if the dependent package is
-; not among the providers (a fully virtual package), or c) nil if the
-; depedent package is a provider but not the first.
+; ========================================
+; Set up hashtable for dependencies without those not installed or
+; shadowed by non-default choice
+
+; Returns the "depends choice" of an automatically dependent package
+; as supported by currently installed packages. Only the first of
+; providers is an automatic dependency. Thus, it returns either a) the
+; depedent package itself if it's the first of its providers, or b)
+; that first of providers if the dependent package is not among the
+; providers (a fully virtual package), or c) nil if the depedent
+; package is a provider but not the first.