Only a comma-at-the-end should make it an incomplete expression

lib/pry/pry_instance.rb

@@ -566,7 +566,7 @@ class Pry
     end
 
     # Assert that a line which ends with a , or a \ is incomplete.
-    str !~ /[,\\]$/
+    str !~ /[,\\]\z/
   rescue SyntaxError => e
     if incomplete_user_input_exception?(e)
       false

test/test_syntax_checking.rb

@@ -44,4 +44,15 @@ describe Pry do
     end
     output.string.should =~ /SyntaxError/
   end
+
+  it "should allow trailing , to continue the line" do
+    pry = Pry.new
+
+    pry.complete_expression?("puts 1, 2,").should == false
+  end
+
+  it "should complete an expression that contains a line ending with a ," do
+    pry = Pry.new
+    pry.complete_expression?("puts 1, 2,\n3").should == true
+  end
 end