Help: Parse Copyright.txt instead of using current year

Configure our Sphinx conf.py with a copyright line extracted from
Copyright.txt instead of using the year in which the documentation is
built.  This will future-proof the reported copyright year range when
building documentation for old versions.

Utilities/Sphinx/CMakeLists.txt

@@ -36,6 +36,15 @@ elseif(NOT SPHINX_EXECUTABLE)
   message(FATAL_ERROR "SPHINX_EXECUTABLE (sphinx-build) is not found!")
 endif()
 
+set(copyright_line_regex "^Copyright (2000-20[0-9][0-9] Kitware.*)")
+file(STRINGS "${CMake_SOURCE_DIR}/Copyright.txt" copyright_line
+  LIMIT_COUNT 1 REGEX "${copyright_line_regex}")
+if(copyright_line MATCHES "${copyright_line_regex}")
+  set(conf_copyright "${CMAKE_MATCH_1}")
+else()
+  set(conf_copyright "Kitware, Inc.")
+endif()
+
 set(conf_docs "${CMake_SOURCE_DIR}/Help")
 set(conf_path "${CMAKE_CURRENT_SOURCE_DIR}")
 set(conf_version "${CMake_VERSION_MAJOR}.${CMake_VERSION_MINOR}.${CMake_VERSION_PATCH}")

Utilities/Sphinx/conf.py.in

@@ -13,7 +13,6 @@ import sys
 import os
 import re
 import glob
-import time
 
 sys.path.insert(0, r'@conf_path@')
 
@@ -21,7 +20,7 @@ source_suffix = '.rst'
 master_doc = 'index'
 
 project = 'CMake'
-copyright = '2000-%s Kitware, Inc.' % time.strftime('%Y')
+copyright = '@conf_copyright@'
 version = '@conf_version@' # feature version
 release = '@conf_release@' # full version string