docs: Place warning at the top of every page in /latest/production.

- Added warning block to dev docs using _templates/layout.html
- Removed copy-pasted warning from install.md and requirements.md
- Removed unreleased tag in docs/conf.py that's no longer used

Useful ref: https://www.sphinx-doc.org/en/master/templating.html

Fixes #13056.

docs/_templates/layout.html

@@ -0,0 +1,26 @@
+{% extends "!layout.html" %}
+{% block document %}
+    <!---
+    # This allows us to insert a warning that appears only on the development
+    # version e.g. to say that something is likely to have changed.
+    # For more info see: https://www.sphinx-doc.org/en/master/templating.html
+    -->
+    {% if pagename == "production/email-gateway" and release.endswith('+git') %}
+    <!--
+    # email-gateway.html page doesn't exist in the stable documentation yet.
+    # This temporary workaround prevents CircleCI failure and should be removed after the next release.
+    -->
+    <div class="admonition warning">
+        <p class="first admonition-title">Warning</p>
+        <p class="last">You are reading a <strong>development version</strong> of the Zulip documentation. These instructions may not correspond to the latest Zulip Server release.
+        See <a class="reference external" href="https://zulip.readthedocs.io/en/stable/production">documentation for the latest stable release</a>.</p>
+    </div>
+    {% elif pagename.split("/")[0] == "production" and release.endswith('+git') %}
+    <div class="admonition warning">
+        <p class="first admonition-title">Warning</p>
+        <p class="last">You are reading a <strong>development version</strong> of the Zulip documentation. These instructions may not correspond to the latest Zulip Server release.
+        See <a class="reference external" href="https://zulip.readthedocs.io/en/stable/{{ pagename }}.html">documentation for the latest stable release</a>.</p>
+    </div>
+    {% endif %}
+    {{ super() }}
+{% endblock %}

docs/conf.py

@@ -54,11 +54,6 @@ version = '2.0+git'
 # The full version, including alpha/beta/rc tags.
 release = '2.0.4+git'
 
-# This allows us to insert a warning that appears only on an unreleased
-# version, e.g. to say that something is likely to have changed.
-if release.endswith('+git'):
-    tags.add('unreleased')
-
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
 #

docs/production/install.md

@@ -1,23 +1,5 @@
 # Production Installation
 
-<!---
-  The `.. only:: unreleased` syntax invokes an rST "directive"
-  called `only`, defined by Sphinx:
-    https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#including-content-based-on-tags
-  It's controlled by `docs/conf.py` through the `tags` object.
--->
-
-```eval_rst
-.. only:: unreleased
-
-   .. warning::
-      You are reading a **development version** of the Zulip documentation.
-      These instructions may not correspond to the latest Zulip Server
-      release.  See `documentation for the latest release`__.
-
-__ https://zulip.readthedocs.io/en/stable/production/install.html
-```
-
 You'll need an Ubuntu or Debian system that satisfies
 [the installation requirements](../production/requirements.html). Alternatively,
 you can use a preconfigured

docs/production/requirements.md

@@ -1,23 +1,5 @@
 # Requirements
 
-<!---
-  The `.. only:: unreleased` syntax invokes an rST "directive"
-  called `only`, defined by Sphinx:
-    https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#including-content-based-on-tags
-  It's controlled by `docs/conf.py` through the `tags` object.
--->
-
-```eval_rst
-.. only:: unreleased
-
-   .. warning::
-      You are reading a **development version** of the Zulip documentation.
-      These instructions may not correspond to the latest Zulip Server
-      release.  See `documentation for the latest release`__.
-
-__ https://zulip.readthedocs.io/en/stable/production/requirements.html
-```
-
 To run a Zulip server, you will need:
 * A dedicated machine or VM
 * A supported OS: