mspec/commands/mspec.rb: formatter for multi_exec

* spec/mspec/lib/mspec/commands/mspec.rb (MSpecMain#multi_exec):
  as multi_exec children must run with yaml formatter, append the
  option for it after other options to override another formatter
  option with a warning if it is given.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58918 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

.travis.yml

@@ -62,7 +62,7 @@ before_script:
 script:
   - "make -s test TESTOPTS=--color=never"
   - "make -s $JOBS test-all TESTOPTS='-q --color=never --job-status=normal'"
-  - "make -s $JOBS test-rubyspec MSPECOPT=-fm"
+  - "make -s $JOBS test-rubyspec MSPECOPT=-j"
 
 # Branch matrix.  Not all branches are Travis-ready so we limit branches here.
 branches:

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

@@ -44,7 +44,6 @@ class MSpecMain < MSpecScript
 
     options.on("-j", "--multi", "Run multiple (possibly parallel) subprocesses") do
       config[:multi] = true
-      config[:options] << "-fy"
     end
 
     options.version MSpec::VERSION do
@@ -94,6 +93,9 @@ class MSpecMain < MSpecScript
 
     require 'mspec/runner/formatters/multi'
     formatter = MultiFormatter.new
+    if config[:formatter]
+      warn "formatter options is ignored due to multi option"
+    end
 
     output_files = []
     processes = [cores, @files.size].min
@@ -105,7 +107,7 @@ class MSpecMain < MSpecScript
         "SPEC_TEMP_DIR" => "rubyspec_temp_#{i}",
         "MSPEC_MULTI" => i.to_s
       }
-      command = argv + ["-o", name]
+      command = argv + ["-fy", "-o", name]
       $stderr.puts "$ #{command.join(' ')}" if $MSPEC_DEBUG
       IO.popen([env, *command], "rb+")
     }