desc: print descriptions directly by formulae instead of cache

We allow passing formulae by URL, file path, etc whose descriptions won't be cached

Closes Homebrew/homebrew#43726.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/cmd/desc.rb

@@ -10,7 +10,10 @@ module Homebrew
 
     if search_type.empty?
       raise FormulaUnspecifiedError if ARGV.named.empty?
-      Descriptions.named(ARGV.formulae.map(&:full_name)).print
+      desc = {}
+      ARGV.formulae.each { |f| desc[f.full_name] = f.desc }
+      results = Descriptions.new(desc)
+      results.print
     elsif search_type.size > 1
       odie "Pick one, and only one, of -s/--search, -n/--name, or -d/--description."
     else

Library/Homebrew/descriptions.rb

@@ -106,22 +106,6 @@ class Descriptions
     end
   end
 
-  # Given an array of formula names, return a {Descriptions} object mapping
-  # those names to their descriptions.
-  def self.named(names)
-    self.ensure_cache
-
-    results = {}
-    unless names.empty?
-      results = names.inject({}) do |accum, name|
-        accum[name] = @cache[name]
-        accum
-      end
-    end
-
-    new(results)
-  end
-
   # Given a regex, find all formulae whose specified fields contain a match.
   def self.search(regex, field = :either)
     self.ensure_cache