diff --git a/CMakeLists.txt b/CMakeLists.txt
index f56beb371..352c1c5b2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -344,6 +344,7 @@ SET(CMake_VERSION_PATCH 0)
 # Releases define a tweak level.
 IF(DEFINED CMake_VERSION_TWEAK)
   SET(CMake_VERSION_IS_RELEASE 1)
+  SET(CMake_VERSION_SOURCE "")
 ELSE()
   SET(CMake_VERSION_IS_RELEASE 0)
 
@@ -352,6 +353,8 @@ ELSE()
   SET(CMake_VERSION_TWEAK
     "${KWSYS_DATE_STAMP_YEAR}${KWSYS_DATE_STAMP_MONTH}${KWSYS_DATE_STAMP_DAY}"
     )
+
+  INCLUDE(${CMake_SOURCE_DIR}/Source/CMakeVersionSource.cmake)
 ENDIF()
 
 # Compute the full version string.
@@ -362,6 +365,9 @@ ENDIF()
 IF(CMake_VERSION_RC)
   SET(CMake_VERSION ${CMake_VERSION}-rc${CMake_VERSION_RC})
 ENDIF()
+IF(CMake_VERSION_SOURCE)
+  SET(CMake_VERSION ${CMake_VERSION}-${CMake_VERSION_SOURCE})
+ENDIF()
 
 # Include the standard Dart testing module
 ENABLE_TESTING()
diff --git a/Source/CMakeVersionSource.cmake b/Source/CMakeVersionSource.cmake
new file mode 100644
index 000000000..05e265c03
--- /dev/null
+++ b/Source/CMakeVersionSource.cmake
@@ -0,0 +1,37 @@
+# Try to identify the current development source version.
+set(CMake_VERSION_SOURCE "")
+if(EXISTS ${CMake_SOURCE_DIR}/.git/HEAD)
+  find_program(GIT_EXECUTABLE NAMES git git.cmd)
+  mark_as_advanced(GIT_EXECUTABLE)
+  if(GIT_EXECUTABLE)
+    execute_process(
+      COMMAND ${GIT_EXECUTABLE} rev-parse --verify -q --short=4 HEAD
+      OUTPUT_VARIABLE head
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+      WORKING_DIRECTORY ${CMake_SOURCE_DIR}
+      )
+    if(head)
+      set(CMake_VERSION_SOURCE "g${head}")
+      execute_process(
+        COMMAND ${GIT_EXECUTABLE} update-index -q --refresh
+        WORKING_DIRECTORY ${CMake_SOURCE_DIR}
+        )
+      execute_process(
+        COMMAND ${GIT_EXECUTABLE} diff-index --name-only HEAD --
+        OUTPUT_VARIABLE dirty
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+        WORKING_DIRECTORY ${CMake_SOURCE_DIR}
+        )
+      if(dirty)
+        set(CMake_VERSION_SOURCE "${CMake_VERSION_SOURCE}-dirty")
+      endif()
+    endif()
+  endif()
+elseif(EXISTS ${CMake_SOURCE_DIR}/CVS/Repository)
+  file(READ ${CMake_SOURCE_DIR}/CVS/Repository repo)
+  set(branch "")
+  if("${repo}" MATCHES "\\.git/")
+    string(REGEX REPLACE ".*\\.git/([^\r\n]*).*" "-\\1" branch "${repo}")
+  endif()
+  set(CMake_VERSION_SOURCE "cvs${branch}")
+endif()
diff --git a/Source/cmDocumentVariables.cxx b/Source/cmDocumentVariables.cxx
index b5830210f..883a7575c 100644
--- a/Source/cmDocumentVariables.cxx
+++ b/Source/cmDocumentVariables.cxx
@@ -259,12 +259,14 @@ void cmDocumentVariables::DefineVariables(cmake* cm)
      ,false, "Variables that Provide Information");
   cm->DefineProperty
     ("CMAKE_VERSION", cmProperty::VARIABLE,
-     "The full version of cmake in major.minor.patch[.tweak] format.",
+     "The full version of cmake in major.minor.patch[.tweak[-id]] format.",
      "This specifies the full version of the CMake executable being run.  "
      "This variable is defined by versions 2.6.3 and higher.  "
      "See variables CMAKE_MAJOR_VERSION, CMAKE_MINOR_VERSION, "
      "CMAKE_PATCH_VERSION, and CMAKE_TWEAK_VERSION "
-     "for individual version components.", false,
+     "for individual version components.  "
+     "The [-id] component appears in non-release versions "
+     "and may be arbitrary text.", false,
      "Variables that Provide Information");
 
   cm->DefineProperty
diff --git a/Tests/FindPackageTest/CMakeLists.txt b/Tests/FindPackageTest/CMakeLists.txt
index 31cf0fce1..74cc11568 100644
--- a/Tests/FindPackageTest/CMakeLists.txt
+++ b/Tests/FindPackageTest/CMakeLists.txt
@@ -232,4 +232,5 @@ TRY_COMPILE(EXPORTER_COMPILED
 MESSAGE(STATUS "Searching for export(PACKAGE) test project")
 SET(CMakeTestExportPackage_DIR "" CACHE FILEPATH
   "Wipe out find results for testing." FORCE)
-FIND_PACKAGE(CMakeTestExportPackage 1.${CMAKE_VERSION} EXACT REQUIRED)
+STRING(REGEX REPLACE "-.*$" "" version ${CMAKE_VERSION})
+FIND_PACKAGE(CMakeTestExportPackage 1.${version} EXACT REQUIRED)