[PR #8069/69bbe874 backport][3.9] 📝 Only show changelog draft for non…

…-releases (#8070)

**This is a backport of PR #8069 as merged into master
(69bbe87).**

## What do these changes do?

$sbj.

## Are there changes in behavior for the user?

RTD for tagged docs builds won't show the changelog draft (which should
be empty in this context).

## Related issue number

N/A

## Checklist

- [x] I think the code is well written
- [x] Unit tests for the changes exist
- [x] Documentation reflects the changes
- [x] If you provide code modification, please add yourself to
`CONTRIBUTORS.txt`
  * The format is <Name> <Surname>.
  * Please keep alphabetical order, the file is sorted by names.
- [x] Add a new news fragment into the `CHANGES/` folder
  * name it `<issue_or_pr_num>.<type>.rst` (e.g. `588.bugfix.rst`)
  * if you don't have an issue number, change it to the pull request
    number after creating the PR
    * `.bugfix`: A bug fix for something the maintainers deemed an
      improper undesired behavior that got corrected to match
      pre-agreed expectations.
    * `.feature`: A new behavior, public APIs. That sort of stuff.
    * `.deprecation`: A declaration of future API removals and breaking
      changes in behavior.
    * `.breaking`: When something public is removed in a breaking way.
      Could be deprecated in an earlier release.
    * `.doc`: Notable updates to the documentation structure or build
      process.
    * `.packaging`: Notes for downstreams about unobvious side effects
      and tooling. Changes in the test invocation considerations and
      runtime assumptions.
    * `.contrib`: Stuff that affects the contributor experience. e.g.
      Running tests, building the docs, setting up the development
      environment.
    * `.misc`: Changes that are hard to assign to any of the above
      categories.
  * Make sure to use full sentences with correct case and punctuation,
    for example:
    ```rst
    Fixed issue with non-ascii contents in doctest text files
    -- by :user:`contributor-gh-handle`.
    ```

    Use the past tense or the present tense a non-imperative mood,
    referring to what's changed compared to the last released version
    of this project.

Co-authored-by: Sviatoslav Sydorenko <wk@sydorenko.org.ua>

CHANGES/8067.doc.rst

@@ -0,0 +1,3 @@
+The Sphinx setup was updated to avoid showing the empty
+changelog draft section in the tagged release documentation
+builds on Read The Docs -- by :user:`webknjaz`.

docs/changes.rst

@@ -4,14 +4,17 @@
 Changelog
 =========
 
-To be included in v\ |release| (if present)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+.. only:: not is_release
 
-.. towncrier-draft-entries:: |release| [UNRELEASED DRAFT]
+   To be included in v\ |release| (if present)
+   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Released versions
-^^^^^^^^^^^^^^^^^
+   .. towncrier-draft-entries:: |release| [UNRELEASED DRAFT]
+
+   Released versions
+   ^^^^^^^^^^^^^^^^^
 
 .. include:: ../CHANGES.rst
+   :start-after: .. towncrier release notes start
 
 .. include:: ../HISTORY.rst

docs/conf.py

@@ -18,6 +18,12 @@
 from pathlib import Path
 
 PROJECT_ROOT_DIR = Path(__file__).parents[1].resolve()
+IS_RELEASE_ON_RTD = (
+    os.getenv("READTHEDOCS", "False") == "True"
+    and os.environ["READTHEDOCS_VERSION_TYPE"] == "tag"
+)
+if IS_RELEASE_ON_RTD:
+    tags.add("is_release")
 
 _docs_path = os.path.dirname(__file__)
 _version_path = os.path.abspath(