[DOCS] Added release-name as a watermark to Docs.

Added a water mark to the role documentation
to make clear to deployers which release they're
working with.

Modified conf.py that adds watermark to the documentation according
to particular branch. If the current branch is master than
watermark is 'Pre-release' and if the current branch is
stable/<release-name> than watermark is <release-name>.

This is a combined implementation based on the following
patches:
- https://review.openstack.org/372565
- https://review.openstack.org/382637
- https://review.openstack.org/384140

Change-Id: Ic3201a200c52d1790103c30350ccfa9b84c6b425

doc/source/conf.py

@@ -23,6 +23,8 @@
 # serve to show the default.
 
 import pbr.version
+import os
+import openstackdocstheme
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -39,7 +41,8 @@ import pbr.version
 # ones.
 extensions = [
     'sphinx.ext.autodoc',
-    'oslosphinx'
+    'oslosphinx',
+    'sphinxmark'
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -129,7 +132,7 @@ todo_include_todos = False
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-# html_theme = 'alabaster'
+html_theme = 'openstackdocs'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
@@ -137,7 +140,7 @@ todo_include_todos = False
 # html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
-# html_theme_path = []
+html_theme_path = [openstackdocstheme.get_html_theme_path()]
 
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
@@ -303,3 +306,16 @@ texinfo_documents = [
 
 # If true, do not generate a @detailmenu in the "Top" node's menu.
 # texinfo_no_detailmenu = False
+
+watermark = os.popen("git branch --contains $(git rev-parse HEAD)\
+| awk -F/ '/stable/ {print $2}'").read().strip(' \n\t').capitalize()
+if watermark == "":
+    watermark = "Pre-release"
+
+# -- Options for sphinxmark -----------------------------------------------
+sphinxmark_enable = True
+sphinxmark_div = 'docs-body'
+sphinxmark_image = 'text'
+sphinxmark_text = watermark
+sphinxmark_text_color = (128, 128, 128)
+sphinxmark_text_size = 70

test-requirements.txt

@@ -11,5 +11,7 @@ ndg-httpsclient>=0.4.2;python_version<'3.0' # BSD
 # this is required for the docs build jobs
 sphinx!=1.3b1,<1.4,>=1.2.1 # BSD
 oslosphinx>=4.7.0 # Apache-2.0
+openstackdocstheme>=1.5.0 # Apache-2.0
 doc8 # Apache-2.0
 reno>=1.8.0 # Apache2
+sphinxmark>=0.1.14  # Apache-2.0