Add changelog fragment and prepare templates.

changelogs/fragments/341-removed-collections.yml

@@ -0,0 +1,3 @@
+minor_changes:
+  - "When rendering the Ansible docsite with the ``stable`` and ``devel`` subcommands, stub pages for removed collections are added
+     (https://github.com/ansible-community/ansible-build-data/pull/459, https://github.com/ansible-community/antsibull-docs/pull/341)."

src/antsibull_docs/data/docsite/ansible-docsite/collection-tombstone.j2

@@ -0,0 +1,23 @@
+{#
+  Copyright (c) Ansible Project
+  GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+  SPDX-License-Identifier: GPL-3.0-or-later
+#}
+
+:orphan:
+
+{% if antsibull_docs_version %}
+.. meta::
+  :antsibull-docs: @{ antsibull_docs_version }@
+
+{% endif %}
+
+.. _plugins_in_@{collection_name}@:
+
+@{collection_name.title()}@
+@{ '=' * (collection_name | column_width) }@
+
+This collection has been removed from Ansible @{ collection_removal_version.major }@.
+
+If you want to continue using this collection, you can install it manually using
+@{ collection | collection_install | rst_code }@.

src/antsibull_docs/data/docsite/ansible-docsite/list_of_collections_by_namespace.rst.j2

@@ -30,6 +30,8 @@ These are the collections documented here in the **@{ namespace }@** namespace.
 
 {% for name in collections | sort %}
 * :ref:`@{ namespace }@.@{ name }@ <plugins_in_@{ namespace }@.@{ name }@>` @{ collection_deprecation_marker(collection_metadata[namespace ~ '.' ~ name]) }@
+{% else %}
+There is no collection in this namespace.
 {% endfor %}
 
 {% if breadcrumbs %}

src/antsibull_docs/data/docsite/simplified-rst/collection-tombstone.j2

@@ -0,0 +1,19 @@
+{#
+  Copyright (c) Ansible Project
+  GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+  SPDX-License-Identifier: GPL-3.0-or-later
+#}
+
+{% if antsibull_docs_version %}
+.. Created with antsibull-docs @{ antsibull_docs_version }@
+{% else %}
+.. Created with antsibull-docs
+{% endif %}
+
+@{collection_name.title()}@
+@{ '=' * (collection_name | column_width) }@
+
+This collection has been removed from Ansible @{ collection_removal_version.major }@.
+
+If you want to continue using this collection, you can install it manually using
+@{ collection | collection_install | rst_code }@.

src/antsibull_docs/data/docsite/simplified-rst/list_of_collections_by_namespace.rst.j2

@@ -29,4 +29,6 @@ These are the collections documented here in the **@{ namespace }@** namespace.
 
 {% for name in collections | sort %}
 * `@{ namespace }@.@{ name }@ <namespace/index.rst>`_
+{% else %}
+There is no collection in this namespace.
 {% endfor %}