Fixed scheduled test runs; Fixed releasing/starting a version docs

Details:

* The test.yml workflow already had a 'schedule' event defined, but only
  in the manual-ci-run branch and not in the master branch. However, it
  turns out that GitHub Actions only runs the schedule event on the
  master branch.

  This change fixes that by adding a new job 'set_matrix' in the test.yml
  workflow that determines the test matrix to run based on the event type.
  For scheduled events, the matrix is set to the full set of environments,
  and otherwise, to the normal smaller set.

  This allowed to abandon the manual-ci-run branch and its PR.

* The description in the development section of the documentation on how
  to release a version or how to start a new version had several issues
  (the most significant one being that it did not account for a stable
  branch that is maintained as a fix stream). This change fixes all
  the issues.

* The description how to release a version missed a step to add the new
  version to RTD. What gets added to RTD are the version tags, and
  the latest and stable versions as defined in RTD. the stable_M.N
  branches do not show up on RTD because that is too confusing.

Signed-off-by: Andreas Maier <andreas.r.maier@gmx.de>

.github/workflows/test.yml

@@ -4,74 +4,100 @@
 name: test
 
 on:
-  # schedule:
-  # # minute hour day_of_month month day_of_week
-  # - cron:  '10 21 * * 0'  # Every sunday at 21:10 UTC
+  schedule:
+    # The schedule event always (and only) runs on the master branch.
+    - # cron (in UTC): minute hour day_of_month month day_of_week
+      cron: '00 03 * * SUN'
   push:
     branches: [ master, stable_1.1 ]
   pull_request:
     branches: [ master, stable_1.1 ]
 
 jobs:
 
+  set_matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.select_matrix.outputs.matrix }}
+    steps:
+    - name: "Select matrix"
+      id: select_matrix
+      # Select full matrix when scheduled or when releasing, and normal matrix
+      # otherwise. The matrix is defined as a JSON string.
+      # TODO: Find a way to define this with less escapes.
+      run: |
+        if [[ "${{ github.event_name }}" == "schedule" || "${{ github.head_ref }}" =~ ^release_ ]]; then \
+          echo "::set-output name=matrix::{ \
+            \"os\": [ \"ubuntu-latest\", \"macos-latest\", \"windows-latest\" ], \
+            \"python-version\": [ \"2.7\", \"3.4\", \"3.5\", \"3.6\", \"3.7\", \"3.8\", \"3.9\" ], \
+            \"package_level\": [ \"minimum\", \"latest\" ], \
+            \"exclude\": [ \
+              { \
+                \"os\": \"macos-latest\", \
+                \"python-version\": \"3.4\", \
+                \"package_level\": \"minimum\" \
+              }, \
+              { \
+                \"os\": \"macos-latest\", \
+                \"python-version\": \"3.4\", \
+                \"package_level\": \"latest\" \
+              }, \
+              { \
+                \"os\": \"windows-latest\", \
+                \"python-version\": \"3.4\", \
+                \"package_level\": \"minimum\" \
+              }, \
+              { \
+                \"os\": \"windows-latest\", \
+                \"python-version\": \"3.4\", \
+                \"package_level\": \"latest\" \
+              } \
+            ] \
+          }"; \
+        else \
+          echo "::set-output name=matrix::{ \
+            \"os\": [ \"ubuntu-latest\" ], \
+            \"python-version\": [ \"2.7\", \"3.4\", \"3.9\" ], \
+            \"package_level\": [ \"minimum\", \"latest\" ], \
+            \"include\": [ \
+              { \
+                \"os\": \"macos-latest\", \
+                \"python-version\": \"3.9\", \
+                \"package_level\": \"latest\" \
+              }, \
+              { \
+                \"os\": \"windows-latest\", \
+                \"python-version\": \"3.8\", \
+                \"package_level\": \"minimum\" \
+              }, \
+              { \
+                \"os\": \"windows-latest\", \
+                \"python-version\": \"3.9\", \
+                \"package_level\": \"minimum\" \
+              }, \
+              { \
+                \"os\": \"windows-latest\", \
+                \"python-version\": \"3.9\", \
+                \"package_level\": \"latest\" \
+              } \
+            ] \
+          }"; \
+        fi
+    - name: Show matrix in JSON
+      run: echo '${{ steps.select_matrix.outputs.matrix }}'
+
   test:
+    needs: set_matrix
     strategy:
       fail-fast: false
       max-parallel: 20
-      # # The matrix for the all-environment pull request:
-      # matrix:
-      #   os: [ubuntu-latest, macos-latest, windows-latest]
-      #   python-version: [2.7, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9]
-      #   package_level: [minimum, latest]
-      #   exclude:
-      #   - os: macos-latest
-      #     python-version: 3.4
-      #     package_level: minimum
-      #   - os: macos-latest
-      #     python-version: 3.4
-      #     package_level: latest
-      #   - os: windows-latest
-      #     python-version: 3.4
-      #     package_level: minimum
-      #   - os: windows-latest
-      #     python-version: 3.4
-      #     package_level: latest
-      # The matrix for normal pull requests:
-      matrix:
-        os: [ubuntu-latest]
-        python-version: [2.7, 3.4, 3.9]
-        package_level: [minimum, latest]
-        include:
-        - os: macos-latest
-          python-version: 3.9
-          package_level: latest
-        - os: windows-latest
-          python-version: 3.8
-          package_level: minimum
-        - os: windows-latest
-          python-version: 3.9
-          package_level: minimum
-        - os: windows-latest
-          python-version: 3.9
-          package_level: latest
+      matrix: ${{ fromJson(needs.set_matrix.outputs.matrix) }}
     runs-on: ${{ matrix.os }}
     steps:
     - name: Checkout repo
       uses: actions/checkout@v2
       with:
         fetch-depth: 0
-    - name: Rebase manual-ci-run to master
-      if: ${{ github.head_ref == 'manual-ci-run' }}
-      run: |
-        echo "Fetching and defining master:"
-        git fetch origin master
-        git branch master FETCH_HEAD
-        echo "Log back to master:"
-        git log master~..HEAD --oneline --decorate
-        echo "Rebasing to master:"
-        git rebase master
-        echo "Log back to master:"
-        git log master~..HEAD --oneline --decorate
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with: