command_helpers.rb: move `set_file_and_dir_locals` from BaseHelpers

Partially fixes (probaby not at all) #705 (Helpers can't be used on
their own)

`set_file_and_dir_locals` is used *only* in commands.

lib/pry/helpers/base_helpers.rb

@@ -42,15 +42,6 @@ class Pry
         end
       end
 
-      def set_file_and_dir_locals(file_name, _pry_=_pry_(), target=target())
-        return if !target or !file_name
-        _pry_.last_file = File.expand_path(file_name)
-        _pry_.inject_local("_file_", _pry_.last_file, target)
-
-        _pry_.last_dir = File.dirname(_pry_.last_file)
-        _pry_.inject_local("_dir_", _pry_.last_dir, target)
-      end
-
       def use_ansi_codes?
         windows_ansi? || ENV['TERM'] && ENV['TERM'] != "dumb"
       end
@@ -104,7 +95,7 @@ class Pry
       end
 
       def mri_19?
-        mri? && RUBY_VERSION =~ /1.9/ 
+        mri? && RUBY_VERSION =~ /1.9/
       end
 
 

lib/pry/helpers/command_helpers.rb

@@ -149,6 +149,16 @@ class Pry
 
         Range.new(a, b)
       end
+
+      def set_file_and_dir_locals(file_name, _pry_=_pry_(), target=target())
+        return if !target or !file_name
+        _pry_.last_file = File.expand_path(file_name)
+        _pry_.inject_local("_file_", _pry_.last_file, target)
+
+        _pry_.last_dir = File.dirname(_pry_.last_file)
+        _pry_.inject_local("_dir_", _pry_.last_dir, target)
+      end
     end
+
   end
 end