aliases inherit options from original, fixes #525

* there was an issue where Pry.config.command_prefix needed to be accessed by CommandSet#find_command
before the config options had loaded -- we just avoid this issue by passing in "" if the config option is not yet defined ;)
This is unlikely to cause any issues, but is a naughty hack all the same.
* added tests to ensure options are inherited

lib/pry/command.rb

@@ -127,7 +127,8 @@ class Pry
       end
 
       def command_regex
-        prefix = convert_to_regex(Pry.config.command_prefix)
+        pr = defined?(Pry.config.command_prefix) ? Pry.config.command_prefix : ""
+        prefix = convert_to_regex(pr)
         prefix = "(?:#{prefix})?" unless options[:use_prefix]
 
         /^#{prefix}#{convert_to_regex(match)}(?!\S)/

lib/pry/command_set.rb

@@ -221,9 +221,12 @@ class Pry
     # @example Pass explicit description (overriding default).
     #   Pry.config.commands.alias_command "lM", "ls -M", :desc => "cutiepie"
     def alias_command(match, action,  options={})
-      options = {
-        :desc => "Alias for `#{action}`",
-      }.merge!(options)
+      original_options = find_command(action).options.dup
+
+      options = original_options.merge!({
+                                          :desc => "Alias for `#{action}`",
+                                          :listing => match
+                                        }).merge!(options)
 
       # ensure default description is used if desc is nil
       desc = options.delete(:desc).to_s

lib/pry/default_commands/introspection.rb

@@ -239,8 +239,8 @@ class Pry
         end
       end
 
-      alias_command "show-method", "show-source", :shellwords => false
-      alias_command "$", "show-source", :shellwords => false
+      alias_command "show-method", "show-source"
+      alias_command "$", "show-source"
 
       command "show-command", "Show the source for CMD." do |*args|
         target = target()

test/test_command_set.rb

@@ -156,6 +156,19 @@ describe Pry::CommandSet do
       run.should == true
     end
 
+    it 'should inherit options from original command' do
+      run = false
+      @set.command('foo', 'stuff', :shellwords => true, :interpolate => false) { run = true }
+
+      @set.alias_command 'bar', 'foo'
+      @set.commands['bar'].options[:shellwords].should == @set.commands['foo'].options[:shellwords]
+      @set.commands['bar'].options[:interpolate].should == @set.commands['foo'].options[:interpolate]
+
+      # however some options should not be inherited
+      @set.commands['bar'].options[:listing].should.not ==  @set.commands['foo'].options[:listing]
+      @set.commands['bar'].options[:listing].should == "bar"
+    end
+
     it 'should be able to specify alias\'s description when aliasing' do
       run = false
       @set.command('foo', 'stuff') { run = true }