Add path-filtering for PRs

.github/workflows/czicompress_cmake.yml

@@ -12,7 +12,14 @@ permissions:
   contents: read
 
 jobs:
+  changes:
+    uses: ./.github/workflows/subproject-changes.yml
+    with:
+      event_name: ${{ github.event_name }}
+
   build-tests:
+    needs: changes
+    if: ${{ needs.changes.outputs.czicompress }}
     defaults:
       run:
         working-directory: ${{github.workspace}}/czicompress

.github/workflows/czicompress_codeql.yml

@@ -16,7 +16,14 @@ permissions:
   security-events: write
 
 jobs:
+  changes:
+    uses: ./.github/workflows/subproject-changes.yml
+    with:
+      event_name: ${{ github.event_name }}
+
   analyze:
+    needs: changes
+    if: ${{ needs.changes.outputs.czicompress == 'true' }}
     name: Analyze CPP
     defaults:
       run:

.github/workflows/czishrink_codeql.yml

@@ -22,6 +22,11 @@ on:
 permissions: read-all
 
 jobs:
+  changes:
+    uses: ./.github/workflows/subproject-changes.yml
+    with:
+      event_name: ${{ github.event_name }}
+
   analyze:
     name: Analyze CziShrink
     defaults:

.github/workflows/czishrink_dotnet.yml

@@ -15,7 +15,14 @@ on:
   workflow_dispatch: {}
 
 jobs:
+  changes:
+    uses: ./.github/workflows/subproject-changes.yml
+    with:
+      event_name: ${{ github.event_name }}
+
   build:
+    needs: changes
+    if: ${{ needs.changes.outputs.czishrink }}
     defaults:
       run:
         working-directory: czishrink

.github/workflows/subproject-changes.yml

@@ -0,0 +1,49 @@
+---
+# A reusable workflow that is used to detect whether code changes
+# are relevant for czishrink and/or czicompress.
+# See
+#  - https://github.com/dorny/paths-filter#examples
+#  - https://docs.github.com/en/actions/using-workflows/reusing-workflows
+name: subproject-changes
+
+# Required permissions
+permissions:
+  pull-requests: read
+
+on:
+  workflow_call:
+    inputs:
+      event_name:
+        required: true
+        type: string
+    outputs:
+      czishrink:
+        description: "true if the change affects czishrink or if event_name is not 'pull_request'; false otherwise"
+        value: ${{ inputs.event_name != 'pull_request' || jobs.changes.outputs.czishrink == 'true' }}
+      czicompress:
+        description: "true if the change affects czicompress or if event_name is not 'pull_request'; false otherwise"
+        value: ${{ inputs.event_name != 'pull_request' || jobs.changes.outputs.czishrink == 'true' }}
+
+jobs:
+  # JOB to run change detection
+  changes:
+    if: ${{ inputs.event_name == 'pull_request' }}
+    runs-on: ubuntu-latest
+    # Set job outputs to values from filter step
+    outputs:
+      czishrink: ${{ steps.filter.outputs.czishrink }}
+      czicompress: ${{ steps.filter.outputs.czicompress }}
+    steps:
+      # For pull requests it's not necessary to checkout the code
+      - uses: dorny/paths-filter@v2
+        id: filter
+        with:
+          filters: |
+            czishrink:
+              - 'czishrink/**'
+              - '.github/**'
+              - '*.yml'
+            czicompress:
+              - '**czicompress**'
+              - '.github/**'
+              - '*.yml'