CMake GitHub workflow: Run the tests of shelving functionality from two

separate steps, that initialize the environment, and run a single test.

* .github/workflows/cmake.yml
  (env): No longer initialize the SVN_EXPERIMENTAL_COMMANDS environment
   variable.
  (Test shelf2, Test shelf3): New steps.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1922653 13f79535-47bb-0310-9956-ffa450edef68

.github/workflows/cmake.yml

@@ -88,7 +88,6 @@ jobs:
     env:
       VCPKG_BINARY_SOURCES: "clear;x-gha,readwrite"
       CMAKE_GENERATOR: ${{ matrix.cmake_generator }}
-      SVN_EXPERIMENTAL_COMMANDS: shelf3
 
     steps:
       - name: Prepare Environment (Windows)
@@ -169,3 +168,17 @@ jobs:
         if: matrix.run_tests
         working-directory: out
         run: ctest --output-on-failure --verbose -C Release --parallel 16
+
+      - name: Test shelf2
+        if: matrix.run_tests
+        working-directory: out
+        env:
+          SVN_EXPERIMENTAL_COMMANDS: shelf2
+        run: ctest -R shelf2 --verbose -C Release
+
+      - name: Test shelf3
+        if: matrix.run_tests
+        working-directory: out
+        env:
+          SVN_EXPERIMENTAL_COMMANDS: shelf3
+        run: ctest -R shelf3 --verbose -C Release