Include Git version string in footer and sidebar (#729)

* Include Git version string in footer.

Try to fetch the current commit description from "git describe" to
dynamically populate the "version" and "release" configuration values.
Add a reference to the template page footer stating the release
information, just below the "Edit on GitHub" link.

* Add a short version number to the sidebar.

In addition to the footer info, include a new snippet into the
navigation sidebar.

Author: acolomb

_templates/layout.html

@@ -3,6 +3,8 @@
 {%- if edit_on_github_url %}
 <div class="body footer-body" role="footer">
     <a class="reference external" href="{{ edit_on_github_url }}" rel="nofollow">{{ _('Edit this page on GitHub') }}</a>
+    <br />
+    <small>Version: {{ release }}</small>
 </div>
 {%- endif %}
 {{ super() }}

_templates/version.html

@@ -0,0 +1,2 @@
+<p>Written for {{ version }}</p>
+<hr />

conf.py

@@ -61,10 +61,13 @@
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
-# The short X.Y version.
-version = 'v1'
 # The full version, including alpha/beta/rc tags.
-release = 'v1'
+try:
+    release = os.popen('git describe --tags --long --always --dirty').read().strip()
+except Exception:
+    release = 'v1'
+# The short X.Y version.
+version = release.partition('-')[0]
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -178,7 +181,16 @@
 #html_use_smartypants = True
 
 # Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
+html_sidebars = {
+    '**': [
+        "about.html",
+        "version.html",
+        "navigation.html",
+        "relations.html",
+        "searchbox.html",
+        "donate.html",
+    ],
+}
 
 # Additional templates that should be rendered to pages, maps page names to
 # template names.