add assign(), fix #1726

lib/pry/config/behavior.rb

@@ -5,6 +5,23 @@ module Pry::Config::Behavior
   ReservedKeyError = Class.new(RuntimeError)
 
   module Builder
+    #
+    # Returns a new Behavior, non-recursively (unlike {#from_hash}).
+    #
+    # @param
+    #   (see #from_hash)
+    #
+    # @return
+    #   (see #from_hash)
+    #
+    def assign(attributes, default = nil)
+      new(default).tap do |behavior|
+        behavior.merge!(attributes)
+      end
+    end
+
+    #
+    # Returns a new Behavior, recursively walking attributes.
     #
     # @param [Hash] attributes
     #   a hash to initialize an instance of self with.

lib/pry/pry_instance.rb

@@ -532,8 +532,7 @@ class Pry
     open_token = @indent.open_delimiters.any? ? @indent.open_delimiters.last :
       @indent.stack.last
 
-    c = Pry::Config.new(nil)
-    c.merge!({
+    c = Pry::Config.assign({
         :object         => object,
         :nesting_level  => binding_stack.size - 1,
         :open_token     => open_token,