brew-upgrade: Fix installation of dependencies

Fixes Homebrew/homebrew#7528.
Closes Homebrew/homebrew#7572.

Library/Homebrew/cmd/upgrade.rb

@@ -20,6 +20,15 @@ module Homebrew extend self
       end
     end
 
+    # Expand the outdated list to include outdated dependencies then sort and
+    # reduce such that dependencies are installed first and installation is not
+    # attempted twice. Sorting is implicit the way `recursive_deps` returns
+    # root dependencies at the head of the list and `uniq` keeps the first
+    # element it encounters and discards the rest.
+    outdated.map!{ |f| f.recursive_deps.reject{ |d| d.installed?} << f }
+    outdated.flatten!
+    outdated.uniq!
+
     if outdated.length > 1
       oh1 "Upgrading #{outdated.length} outdated package#{outdated.length.plural_s}, with result:"
       puts outdated.map{ |f| "#{f.name} #{f.version}" } * ", "