Add version changed note for -m tinkering with sys.argv[0] during the search process
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 0199f9f..d458ddb 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -118,6 +118,8 @@
 
    .. versionchanged:: 2.7
       Supply the package name to run a ``__main__`` submodule.
+      sys.argv[0] is now set to ``"-m"`` while searching for the module
+      (it was previously incorrectly set to ``"-c"``)
 
 
 .. describe:: -