updated rename_command() to accept either actual command name or listing name, tests also updated

lib/pry/command_set.rb

@@ -242,8 +242,9 @@ class Pry
       commands[new_name].description = desc
     end
 
-    # Rename a command. You must use the actual name of the command,
-    # not the listing name.
+    # Rename a command. Accepts either actual name or listing name for
+    # the `old_name`.
+    # `new_name` must be the actual name of the new command.
     # @param [String, Regexp] new_name The new name for the command.
     # @param [String, Regexp] old_name The command's current name.
     # @param [Hash] options The optional configuration parameters,
@@ -252,18 +253,18 @@ class Pry
     # @example Renaming the `ls` command and changing its description.
     #   Pry.config.commands.rename "dir", "ls", :description => "DOS friendly ls"
     def rename_command(new_name, old_name, options={})
-      raise ArgumentError, "A command called '#{old_name}' was not found!" if !commands[old_name]
-      
+      cmd = find_command_by_name_or_listing(old_name)
+
       options = {
         :listing     => new_name,
-        :description => commands[old_name].description
+        :description => cmd.description
       }.merge!(options)
-      
-      commands[new_name] = commands[old_name]
+
+      commands[new_name] = cmd.dup
       commands[new_name].name = new_name
       commands[new_name].description = options.delete(:description)
       commands[new_name].options.merge!(options)
-      commands.delete(old_name)
+      commands.delete(cmd.name)
     end
 
     # Runs a command.

test/test_command_set.rb

@@ -280,9 +280,16 @@ describe Pry::CommandSet do
       run.should == true
     end
 
-    it 'should not accept listing name when renaming a command' do
-      @set.command('foo', "", :listing => 'love') { }
-      lambda { @set.rename_command('bar', 'love') }.should.raise ArgumentError
+    it 'should accept listing name when renaming a command' do
+      run = false
+      @set.command('foo', "", :listing => 'love') { run = true }
+      @set.rename_command('bar', 'love')
+      @set.run_command(@ctx, 'bar')
+      run.should == true
+    end
+
+    it 'should raise exception trying to rename non-existent command' do
+      lambda { @set.rename_command('bar', 'foo') }.should.raise ArgumentError
     end
 
     it 'should make old command name inaccessible' do
@@ -291,6 +298,7 @@ describe Pry::CommandSet do
       lambda { @set.run_command(@ctx, 'foo') }.should.raise Pry::NoCommandError
     end
 
+
     it 'should be able to pass in options when renaming command' do
       desc    = "hello"
       listing = "bing"