Add sphinx.version_info for better programmatic check of the Sphinx version.

doc/ext/appapi.rst

@@ -462,6 +462,22 @@ registered event handlers.
    .. versionadded:: 0.5
 
 
+Checking the Sphinx version
+---------------------------
+
+.. currentmodule:: sphinx
+
+Use this to adapt your extension to API changes in Sphinx.
+
+.. data:: version_info
+
+   A tuple of five elements; for Sphinx version 1.2.1 beta 3 this would be
+   ``(1, 2, 1, 'beta', 3)``.
+
+   .. versionadded:: 1.2
+      Before version 1.2, check the string ``sphinx.__version__``.
+
+
 .. _template-bridge:
 
 The template bridge

sphinx/__init__.py

@@ -17,6 +17,9 @@ from os import path
 
 __version__  = '1.2b3'
 __released__ = '1.2b3'  # used when Sphinx builds its own docs
+# version info for better programmatic use
+# possible values for 3rd element: 'alpha', 'beta', 'rc', 'final'
+version_info = (1, 2, 0, 'beta', 3)
 
 package_dir = path.abspath(path.dirname(__file__))