Avoid nil in URL specs

Library/Homebrew/download_strategy.rb

@@ -4,13 +4,7 @@
 class AbstractDownloadStrategy
   def initialize name, package
     @url = package.url
-    @specs = package.specs
-
-    case @specs
-    when Hash
-      @spec = @specs.keys.first # only use first spec
-      @ref = @specs.values.first
-    end
+    @spec, @ref = package.specs.dup.shift
   end
 
   def expand_safe_system_args args

Library/Homebrew/formula.rb

@@ -698,7 +698,7 @@ def build
       @build ||= BuildOptions.new(ARGV.options_only)
     end
 
-    def url val=nil, specs=nil
+    def url val=nil, specs={}
       if val.nil?
         return @stable.url if @stable
         return @url if @url
@@ -724,7 +724,7 @@ def devel &block
       @devel.instance_eval(&block)
     end
 
-    def head val=nil, specs=nil
+    def head val=nil, specs={}
       return @head if val.nil?
       @head ||= HeadSoftwareSpec.new
       @head.url(val, specs)

Library/Homebrew/formula_support.rb

@@ -9,6 +9,7 @@ def initialize url=nil, version=nil
     @url = url
     @version = version
     @mirrors = []
+    @specs = {}
   end
 
   def download_strategy
@@ -42,13 +43,11 @@ def #{cksum}(val=nil)
     }
   end
 
-  def url val=nil, specs=nil
+  def url val=nil, specs={}
     return @url if val.nil?
     @url = val
-    unless specs.nil?
-      @using = specs.delete :using
-      @specs = specs
-    end
+    @using = specs.delete(:using)
+    @specs.merge!(specs)
   end
 
   def version val=nil

Library/Homebrew/test/test_formula.rb

@@ -82,9 +82,9 @@ def test_formula_specs
     assert_equal 'file:///foo.com/testball-0.2.tbz', f.devel.url
     assert_equal 'https://github.com/mxcl/homebrew.git', f.head.url
 
-    assert_nil f.stable.specs
-    assert_nil f.bottle.specs
-    assert_nil f.devel.specs
+    assert_empty f.stable.specs
+    assert_empty f.bottle.specs
+    assert_empty f.devel.specs
     assert_equal({ :tag => 'foo' }, f.head.specs)
 
     assert_equal CurlDownloadStrategy, f.stable.download_strategy