Don't use 'obj == nil'

Library/Homebrew/cmd/create.rb

@@ -125,7 +125,7 @@ class FormulaCreator
 
     <% if  mode == :cmake %>
       depends_on 'cmake' => :build
-    <% elsif  mode == nil %>
+    <% elsif  mode.nil? %>
       # depends_on 'cmake' => :build
     <% end  %>
       depends_on :x11 # if your formula requires any X11/XQuartz components

Library/Homebrew/utils.rb

@@ -218,7 +218,7 @@ def inreplace paths, before=nil, after=nil
     f = File.open(path, 'r')
     s = f.read
 
-    if before == nil and after == nil
+    if before.nil? && after.nil?
       s.extend(StringInreplaceExtension)
       yield s
     else