ci: Update the CI to only run tests if relevant

.github/workflows/test.yaml

@@ -48,7 +48,21 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       matrix: ${{ env.MATRIX }}
+      code_change: ${{ steps.filter.outputs.code }}
     steps:
+      - uses: actions/checkout@v4
+        if: github.event_name != 'pull_request'
+      - name: Check for code changes
+        uses: dorny/paths-filter@v3
+        id: filter
+        with:
+          filters: |
+            code:
+              - 'datashader/**'
+              - 'examples/**'
+              - 'pixi.toml'
+              - 'pyproject.toml'
+              - '.github/workflows/test.yaml'
       - name: Set matrix option
         run: |
           if [[ '${{ github.event_name }}' == 'workflow_dispatch' ]]; then
@@ -98,6 +112,7 @@ jobs:
     name: unit:${{ matrix.environment }}:${{ matrix.os }}
     needs: [pre_commit, setup, pixi_lock]
     runs-on: ${{ matrix.os }}
+    if: needs.setup.outputs.code_change == 'true'
     strategy:
       fail-fast: false
       matrix: ${{ fromJson(needs.setup.outputs.matrix) }}
@@ -126,6 +141,7 @@ jobs:
     name: core:${{ matrix.environment }}:${{ matrix.os }}
     needs: [pre_commit, setup, pixi_lock]
     runs-on: ${{ matrix.os }}
+    if: needs.setup.outputs.code_change == 'true'
     strategy:
       fail-fast: false
       matrix:
@@ -139,3 +155,13 @@ jobs:
       - name: Test Unit
         run: |
           pixi run -e ${{ matrix.environment }} test-unit
+
+  result_test_suite:
+    name: result:test
+    needs: [unit_test_suite, core_test_suite]
+    if: always()
+    runs-on: ubuntu-latest
+    steps:
+      - name: check for failures
+        if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
+        run: echo job failed && exit 1