Add a matrix run to test also with datalad-next installed (patching d…

…atalad)

templates/.github/workflows/test-{{extension.name}}-{{datalad_branch}}.yaml

@@ -28,6 +28,7 @@ jobs:
         # name mimics the one in .travis.yml for datalad build introduced in
         # https://github.com/datalad/datalad/pull/4640
         annex-install-scenario: [neurodebian, datalad-git-annex-latest]
+        datalad-install-scenario: [plain, with-datalad-next-release]
       fail-fast: false
 
     steps:
@@ -63,6 +64,9 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install https://github.com/datalad/datalad/archive/{{ datalad_branch }}.zip
+    - name: Install datalad-next
+      if: matrix.datalad-install-scenario == 'with-datalad-next-release' && datalad_branch == 'maint'
+      run: pip install datalad-next
     - name: Install {{ extension.name }} extension from PyPI ([devel,test,tests])
       run: |
         pip install {{ extension.pypi }}[devel,test,tests]