Use ChildProcess to spawn detached processes

As of childprocess 0.5.6, it is possible to check the exit status
of a ChildProcess without an error being thrown.

Author: jawshooah

Diff for: lib/overcommit/subprocess.rb

@@ -32,8 +32,12 @@ def spawn(args)
       # Spawns a new process in the background using the given array of
       # arguments (the first element is the command).
       def spawn_detached(args)
-        # Dissociate process from parent's input/output streams
-        Process.detach(Process.spawn({}, *args, [:in, :out, :err] => '/dev/null'))
+        process = ChildProcess.build(*args)
+        process.detach = true
+
+        assign_output_streams(process)
+
+        process.start
       end
 
       private

Diff for: lib/overcommit/utils.rb

@@ -129,7 +129,7 @@ def execute(args)
       # which we do not need to know the result.
       #
       # @param args [Array<String>]
-      # @return [Thread] thread watching the resulting child process
+      # @return [ChildProcess] detached process spawned in the background
       def execute_in_background(args)
         if args.include?('|')
           raise Overcommit::Exceptions::InvalidCommandArgs,

Diff for: spec/overcommit/utils_spec.rb

@@ -163,7 +163,7 @@
     end
 
     it 'executes the command' do
-      wait_until { subject.stop? } # Make sure process terminated before checking
+      wait_until { subject.exited? } # Make sure process terminated before checking
       File.exist?('some-file').should == true
     end
   end