[doc] Support versioned documents with RTD(ReadTheDocs)

docs/_templates/versions.html

@@ -0,0 +1,55 @@
+{% if READTHEDOCS or display_lower_left %}
+{# Add rst-badge after rst-versions for small badge style. #}
+  <div class="rst-versions" data-toggle="rst-versions" role="note" aria-label="versions">
+    <span class="rst-current-version" data-toggle="rst-current-version">
+      <span class="fa fa-book"> Read the Docs</span>
+      v: {{ current_version }}
+      <span class="fa fa-caret-down"></span>
+    </span>
+    <div class="rst-other-versions">
+      {% if languages|length >= 1 %}
+      <dl>
+        <dt>{{ _('Languages') }}</dt>
+        {% for slug, url in languages %}
+          {% if slug == current_language %} <strong> {% endif %}
+          <dd><a href="{{ url }}">{{ slug }}</a></dd>
+          {% if slug == current_language %} </strong> {% endif %}
+        {% endfor %}
+      </dl>
+      {% endif %}
+      {% if versions|length >= 1 %}
+      <dl>
+        <dt>{{ _('Versions') }}</dt>
+        {% for slug, url in versions %}
+          {% if slug == current_version %} <strong> {% endif %}
+          <dd><a href="{{ url }}">{{ slug }}</a></dd>
+          {% if slug == current_version %} </strong> {% endif %}
+        {% endfor %}
+      </dl>
+      {% endif %}
+      {% if downloads|length >= 1 %}
+      <dl>
+        <dt>{{ _('Downloads') }}</dt>
+        {% for type, url in downloads %}
+          <dd><a href="{{ url }}">{{ type }}</a></dd>
+        {% endfor %}
+      </dl>
+      {% endif %}
+      {% if READTHEDOCS %}
+      <dl>
+        <dt>{{ _('On Read the Docs') }}</dt>
+          <dd>
+            <a href="//{{ PRODUCTION_DOMAIN }}/projects/{{ slug }}/?fromdocs={{ slug }}">{{ _('Project Home') }}</a>
+          </dd>
+          <dd>
+            <a href="//{{ PRODUCTION_DOMAIN }}/builds/{{ slug }}/?fromdocs={{ slug }}">{{ _('Builds') }}</a>
+          </dd>
+      </dl>
+      {% endif %}
+      <hr/>
+      {% trans %}Free document hosting provided by <a href="http://www.readthedocs.org">Read the Docs</a>.{% endtrans %}
+ 
+    </div>
+  </div>
+{% endif %}
+ 

pom.xml

@@ -182,6 +182,7 @@ under the License.
                         <exclude>**/*.md</exclude>
                         <exclude>docs/Makefile</exclude>
                         <exclude>docs/make.bat</exclude>
+                        <exclude>docs/_templates/version.html</exclude>
                         <!-- Tests -->
                         <exclude>**/*.txt</exclude>
                     </excludes>