cmake_minimum_required required by cmake-2.6

With the latest cmake-2.6 version, I'm getting this warning:

CMake Warning (dev) in CMakeLists.txt:
  No cmake_minimum_required command is present. A line of code such as

    cmake_minimum_required(VERSION 2.6)

  should be added at the top of the file. The version specified may be lower
  if you wish to support older CMake versions for this project. For more
  information run "cmake --help-policy CMP0000".
This warning is for project developers. Use -Wno-dev to suppress it.

-- Configuring done
-- Generating done
-- Build files have been written to: /home/michael/bzr/partimage-ng/build
michael@pluto:~/bzr/partimage-ng/build$ cmake --help-policy CMP0000
cmake version 2.6-patch 0
------------------------------------------------------------------------------

  CMP0000
       A minimum required CMake version must be specified.

       CMake requires that projects specify the version of CMake to which
       they have been written. This policy has been put in place so users
       trying to build the project may be told when they need to update their
       CMake. Specifying a version also helps the project build with CMake
       versions newer than that specified. Use the cmake_minimum_required
       command at the top of your main CMakeLists.txt file:

         cmake_minimum_required(VERSION <major>.<minor>)

       where "<major>.<minor>" is the version of CMake you want to support
       (such as "2.6"). The command will ensure that at least the given
       version of CMake is running and help newer versions be compatible with
       the project. See documentation of cmake_minimum_required for details.

       Note that the command invocation must appear in the CMakeLists.txt
       file itself; a call in an included file is not sufficient. However,
       the cmake_policy command may be called to set policy CMP0000 to OLD or
       NEW behavior explicitly. The OLD behavior is to silently ignore the
       missing invocation. The NEW behavior is to issue an error instead of
       a warning. An included file may set CMP0000 explicitly to affect how
       this policy is enforced for the main CMakeLists.txt file.

       This policy was introduced in CMake version 2.6.0.