Added status command to reference implementation and REP. Here is an 
example output over bzr, git, hg and svn subdirs:
$ rosenv status test3 --untracked
+N test3/bzr-test/ bar
  M test3/bzr-test/ foo.txt
  M test3/ias_common/CMakeLists.txt
A  test3/ias_common/foogit
  M test3/ias_common/stack.xml
M  test3/geometry_tutorials/turtle_tf/CMakeLists.txt
A  test3/geometry_tutorials/bla.hg
!  test3/geometry_tutorials/stack.xml
?  test3/geometry_tutorials/bar.txt
?  test3/geometry_tutorials/foo.txt
?       test3/test/common_msgs/CMakeLists.txt.rej
?       test3/test/common_msgs/.rosinstall
?       test3/test/common_msgs/CMakeLists.txt.orig
A       test3/test/common_msgs/foosvn
M       test3/test/common_msgs/CMakeLists.txt


A little confusing. Not sure whether it's worth bothering to unify the 
looks a bit.