Copyright.txt: Add test to check year range

Add a CMake.Copyright test that, when the CMake version number knows the
year (as it does in development versions), checks that Copyright.txt has
been updated with the current version year.

Tests/CMakeCopyright.cmake

@@ -0,0 +1,22 @@
+if(CMAKE_VERSION MATCHES "\\.(20[0-9][0-9])[0-9][0-9][0-9][0-9](-|$)")
+  set(version_year "${CMAKE_MATCH_1}")
+  set(copyright_line_regex "^Copyright 2000-(20[0-9][0-9]) Kitware")
+  file(STRINGS "${CMAKE_CURRENT_LIST_DIR}/../Copyright.txt" copyright_line
+    LIMIT_COUNT 1 REGEX "${copyright_line_regex}")
+  if(copyright_line MATCHES "${copyright_line_regex}")
+    set(copyright_year "${CMAKE_MATCH_1}")
+    if(copyright_year LESS version_year)
+      message(FATAL_ERROR "Copyright.txt contains\n"
+        " ${copyright_line}\n"
+        "but the current version year is ${version_year}.")
+    else()
+      message(STATUS "PASSED: Copyright.txt contains\n"
+        " ${copyright_line}\n"
+        "and the current version year is ${version_year}.")
+    endif()
+  else()
+    message(FATAL_ERROR "Copyright.txt has no Copyright line of expected format!")
+  endif()
+else()
+  message(STATUS "SKIPPED: CMAKE_VERSION does not know the year: ${CMAKE_VERSION}")
+endif()

Tests/CMakeLists.txt

@@ -161,6 +161,9 @@ if(BUILD_TESTING)
     set(CMAKE_LONG_TEST_TIMEOUT 1500)
   endif()
 
+  add_test(NAME CMake.Copyright
+    COMMAND cmake -P ${CMAKE_CURRENT_SOURCE_DIR}/CMakeCopyright.cmake)
+
   # add a bunch of standard build-and-test style tests
   ADD_TEST_MACRO(CommandLineTest CommandLineTest)
   ADD_TEST_MACRO(FindPackageTest FindPackageTest)