docs: building (PDF) books / build user book

BTW: cleaned up Makefile target help

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

utils/site-python/sphinx_build_tools.py

@@ -0,0 +1,48 @@
+# -*- coding: utf-8; mode: python -*-
+"""Implement some sphinx-build tools.
+
+"""
+
+import os
+import sys
+from sphinx.util.pycompat import execfile_
+
+# ------------------------------------------------------------------------------
+def load_sphinx_config(namespace):
+# ------------------------------------------------------------------------------
+
+    u"""Load an additional configuration file into *namespace*.
+
+    The name of the configuration file is taken from the environment
+    ``SPHINX_CONF``. The external configuration file extends (or overwrites) the
+    configuration values from the origin ``conf.py``.  With this you are able to
+    maintain *build themes*.  To your docs/conf.py add::
+
+        from sphinx_build_tools import load_sphinx_config
+        ...
+
+        # Since loadConfig overwrites settings from the global namespace, it has to be
+        # the last statement in the conf.py file
+
+        load_sphinx_config(globals())
+
+    """
+
+    config_file = os.environ.get("SPHINX_CONF", None)
+    if (config_file is not None
+        and os.path.normpath(namespace["__file__"]) != os.path.normpath(config_file) ):
+        config_file = os.path.abspath(config_file)
+
+        if os.path.isfile(config_file):
+            sys.stdout.write(
+                "load additional sphinx-config: %s\n"
+                % config_file)
+            config = namespace.copy()
+            config['__file__'] = config_file
+            execfile_(config_file, config)
+            del config['__file__']
+            namespace.update(config)
+        else:
+            sys.stderr.write(
+                "WARNING: additional sphinx-config not found: %s\n"
+                % config_file)