Formulary: add ::map to map formula refs

Library/Homebrew/formulary.rb

@@ -395,6 +395,8 @@ module Formulary
   )
     raise ArgumentError, "Formulae must have a ref!" unless ref
 
+    ref = @ref_mappings[ref] if @ref_mappings.present? && @ref_mappings.key?(ref)
+
     cache_key = "#{ref}-#{spec}-#{alias_path}-#{from}"
     if factory_cached? && cache[:formulary_factory] &&
        cache[:formulary_factory][cache_key]
@@ -411,6 +413,19 @@ module Formulary
     formula
   end
 
+  # Register a reference mapping. This mapping will be used by {Formulary::factory}
+  # to allow certain references to be substituted for another string before
+  # being retrived. For example, to map `foo` to the `bar` formula:
+  # <pre>Formulary.map "foo", to: "bar"
+  # Formulary.factory "bar" # returns the bar formula
+  # </pre>
+  # @param ref the string to map.
+  # @param :to the target reference to which `ref` should be mapped.
+  def self.map(ref, to:)
+    @ref_mappings ||= {}
+    @ref_mappings[ref] = to
+  end
+
   # Return a {Formula} instance for the given rack.
   #
   # @param spec when nil, will auto resolve the formula's spec.

Library/Homebrew/test/formulary_spec.rb

@@ -205,6 +205,23 @@ describe Formulary do
     end
   end
 
+  describe "::map" do
+    before do
+      formula_path.dirname.mkpath
+      formula_path.write formula_content
+    end
+
+    it "maps a reference to a new Formula" do
+      expect {
+        described_class.factory("foo")
+      }.to raise_error(FormulaUnavailableError)
+
+      described_class.map "foo", to: formula_name
+
+      expect(described_class.factory("foo")).to be_kind_of(Formula)
+    end
+  end
+
   specify "::from_contents" do
     expect(described_class.from_contents(formula_name, formula_path, formula_content)).to be_kind_of(Formula)
   end