Enable "-f" option in multi_exec mode

Make `MultiFormatter` a module and extend the formatter specified
by "-f" option.

spec/mspec/lib/mspec/commands/mspec.rb

@@ -90,8 +90,7 @@ class MSpecMain < MSpecScript
 
   def multi_exec(argv)
     require 'mspec/runner/formatters/multi'
-    formatter = MultiFormatter.new
-    warn "formatter options is ignored due to multi option" if config[:formatter]
+    formatter = config_formatter.extend(MultiFormatter)
 
     require 'mspec/runner/parallel'
     processes = cores(@files.size)

spec/mspec/lib/mspec/runner/formatters/dotted.rb

@@ -97,6 +97,16 @@ class DottedFormatter
     end
   end
 
+  # Callback for the MSpec :start event. Calls :after event.
+  def start
+    after
+  end
+
+  # Callback for the MSpec :unload event. Calls :after event.
+  def unload
+    after
+  end
+
   # Callback for the MSpec :finish event. Prints a description
   # and backtrace for every exception that occurred while
   # evaluating the examples.

spec/mspec/lib/mspec/runner/formatters/multi.rb

@@ -1,13 +1,23 @@
-require 'mspec/runner/formatters/spinner'
+module MultiFormatter
+  def self.extend_object(obj)
+    super
+    obj.multi_initialize
+  end
 
-class MultiFormatter < SpinnerFormatter
-  def initialize(out=nil)
-    super(out)
+  def multi_initialize
     @counter = @tally = Tally.new
     @timer = TimerAction.new
     @timer.start
   end
 
+  def register
+    super
+
+    MSpec.register :start, self
+    MSpec.register :unload, self
+    MSpec.unregister :before, self
+  end
+
   def aggregate_results(files)
     require 'yaml'
 

spec/mspec/lib/mspec/utils/script.rb

@@ -125,12 +125,7 @@ class MSpecScript
     require 'mspec/runner/formatters/file'
     require 'mspec/runner/filters'
 
-    if config[:formatter].nil?
-      config[:formatter] = STDOUT.tty? ? SpinnerFormatter : @files.size < 50 ? DottedFormatter : FileFormatter
-    end
-
-    if config[:formatter]
-      formatter = config[:formatter].new(config[:output])
+    if formatter = config_formatter
       formatter.register
       MSpec.store :formatter, formatter
     end
@@ -149,6 +144,14 @@ class MSpecScript
     custom_register
   end
 
+  # Makes a formatter specified by :formatter option.
+  def config_formatter
+    if config[:formatter].nil?
+      config[:formatter] = STDOUT.tty? ? SpinnerFormatter : @files.size < 50 ? DottedFormatter : FileFormatter
+    end
+    config[:formatter].new(config[:output])
+  end
+
   # Callback for enabling custom actions, etc. This version is a
   # no-op. Provide an implementation specific version in a config
   # file. Called by #register.