FindGit: support version number

Modules/FindGit.cmake

@@ -1,6 +1,7 @@
 # The module defines the following variables:
 #   GIT_EXECUTABLE - path to git command line client
 #   GIT_FOUND - true if the command line client was found
+#   GIT_VERSION_STRING - the version of git found (since CMake 2.8.8)
 # Example usage:
 #   find_package(Git)
 #   if(GIT_FOUND)
@@ -9,6 +10,7 @@
 
 #=============================================================================
 # Copyright 2010 Kitware, Inc.
+# Copyright 2012 Rolf Eike Beer <[email protected]>
 #
 # Distributed under the OSI-approved BSD License (the "License");
 # see accompanying file Copyright.txt for details.
@@ -40,8 +42,21 @@ find_program(GIT_EXECUTABLE
   )
 mark_as_advanced(GIT_EXECUTABLE)
 
+if(GIT_EXECUTABLE)
+  execute_process(COMMAND ${GIT_EXECUTABLE} --version
+                  OUTPUT_VARIABLE git_version
+                  ERROR_QUIET
+                  OUTPUT_STRIP_TRAILING_WHITESPACE)
+  if (git_version MATCHES "^git version [0-9]")
+    string(REPLACE "git version " "" GIT_VERSION_STRING "${git_version}")
+  endif()
+  unset(git_version)
+endif(GIT_EXECUTABLE)
+
 # Handle the QUIETLY and REQUIRED arguments and set GIT_FOUND to TRUE if
 # all listed variables are TRUE
 
 include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
-find_package_handle_standard_args(Git DEFAULT_MSG GIT_EXECUTABLE)
+find_package_handle_standard_args(Git
+                                  REQUIRED_VARS GIT_EXECUTABLE
+                                  VERSION_VAR GIT_VERSION_STRING)