Ensure repo checkout is unshallow in RTD builds for SCM versioning

.readthedocs.yaml

@@ -2,15 +2,17 @@
 # Read the Docs configuration file
 # See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
 
-# Required
 version: 2
 
-# Set the version of Python and other tools you might need
 build:
   os: ubuntu-22.04
   tools:
     python: "3"
   jobs:
+    post_checkout:
+      # RTD defaults to a depth of 50 but Toga versioning may require
+      # much more git history to accurately determine the SCM version
+      - git fetch --unshallow
     pre_build:
       - tox -e docs-lint
 
@@ -24,11 +26,11 @@ sphinx:
 formats:
    - pdf
 
-# Python requirements required to build your docs
+# Install extras for build - dev is needed to run tox
 python:
   install:
   - method: pip
     path: core
     extra_requirements:
-      - docs
       - dev
+      - docs

changes/2019.misc.rst

@@ -0,0 +1 @@
+The Toga repository checkout for Read the Docs builds is now made unshallow to ensure accurate SCM versioning.