Move Pry#save_history to Pry.save_history.

This is for consistency with Pry.load_history

lib/pry/default_commands/context.rb

@@ -67,7 +67,7 @@ class Pry
       alias_command "!!@", "exit-all", ""
 
       command "exit-program", "End the current program. Aliases: quit-program, !!!" do
-        Pry.active_instance.save_history if Pry.config.history.should_save
+        Pry.save_history if Pry.config.history.should_save
         exit
       end
 

lib/pry/pry_class.rb

@@ -139,10 +139,21 @@ class Pry
 
   # Load Readline history if required.
   def self.load_history
-    history_file = File.expand_path(Pry.config.history.file)
     Readline::HISTORY.push(*File.readlines(history_file).map(&:chomp)) if File.exists?(history_file)
   end
 
+  # Save Readline history if required.
+  def self.save_history
+    File.open(history_file, 'w') do |f|
+      f.write Readline::HISTORY.to_a.join("\n")
+    end
+  end
+
+  # Get the full path of the history_path for pry.
+  def self.history_file
+    File.expand_path(Pry.config.history.file)
+  end
+
   # @return [Boolean] Whether this is the first time a Pry session has
   #   been started since loading the Pry class.
   def self.initial_session?

lib/pry/pry_instance.rb

@@ -149,7 +149,7 @@ class Pry
       throw :breakout, break_data
     end
 
-    save_history if Pry.config.history.should_save && finished_top_level_session?
+    Pry.save_history if Pry.config.history.should_save && finished_top_level_session?
 
     return_value
   end
@@ -406,14 +406,6 @@ class Pry
     !@suppress_output || last_result_is_exception?
   end
 
-  # Save readline history to a file.
-  def save_history
-    history_file = File.expand_path(Pry.config.history.file)
-    File.open(history_file, 'w') do |f|
-      f.write Readline::HISTORY.to_a.join("\n")
-    end
-  end
-
   # Returns the appropriate prompt to use.
   # This method should not need to be invoked directly.
   # @param [Boolean] first_line Whether this is the first line of input