Don't run CI unless there are salient code changes (#434)

* Don't run CI unless there are salient code changes

* Key off of file extensions, not directories

* Also filter unit test builds

* Make a change to a non-HPKE component

* Properly quote YAML strings

* Require a specific path

* Touch the file again

* Revert top-level filters

* Revert all changes

* Trigger on changes to workflows

* Trigger on code changes

* Reinstate filters

* Try a different strategy

* Trigger on workflow changes

* Fix copy/paste error

* Fix copy/paste error

* Touch an hpke file

* Revert code changes

* Use the crypto matrix to guide CI jobs

* Correct 'needs'

* Restore accidentally deleted checkout step

.github/workflows/main_ci.yml

@@ -4,9 +4,17 @@ on:
   push:
     branches:
       - main
+    paths:
+      - ".github/**"
+      - "**.cpp"
+      - "**.h"
   pull_request:
     branches:
       - main
+    paths:
+      - ".github/**"
+      - "**.cpp"
+      - "**.h"
 
 env:
   CMAKE_BUILD_PARALLEL_LEVEL: 3
@@ -15,8 +23,33 @@ env:
   CMAKE_TOOLCHAIN_FILE: ${{ github.workspace }}/vcpkg/scripts/buildsystems/vcpkg.cmake
 
 jobs:
+  choose_crypto_matrix:
+    name: Choose crypto libraries to test with
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+    - uses: dorny/paths-filter@v3
+      id: filterV
+      with:
+        filters: |
+          hpke:
+            - 'lib/hpke/include/**'
+            - 'lib/hpke/src/**'
+            - 'lib/hpke/test/**'
+ 
+    - id: set-matrix 
+      run: |
+        if [ ${{ steps.filter.outputs.hpke }} = "true" ];
+        then
+          echo "matrix=[\"openssl_1.1\",\"openssl_3\",\"boringssl\"]" >> $GITHUB_OUTPUT;
+        else
+          echo "matrix=[\"openssl_3\"]" >> $GITHUB_OUTPUT
+        fi
+
   formatting-check:
     name: Formatting Check
+    needs: choose_crypto_matrix
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
@@ -29,13 +62,13 @@ jobs:
         fallback-style: 'Mozilla'
 
   build-and-unit-test:
-    needs: formatting-check
+    needs: [formatting-check, choose_crypto_matrix]
     name: Build and test
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         os: [windows-latest, ubuntu-latest, macos-latest]
-        crypto: [openssl_1.1, openssl_3, boringssl]
+        crypto: ${{ fromJson(needs.choose_crypto_matrix.outputs.matrix )}}
 
     env:
       CRYPTO_DIR: "./alternatives/${{ matrix.crypto }}"
@@ -108,12 +141,12 @@ jobs:
 
   clang-tidy:
     if: github.event.pull_request.draft == false
-    needs: build-and-unit-test
+    needs: [build-and-unit-test, choose_crypto_matrix]
     name: Build with clang-tidy
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        crypto: [openssl_1.1, openssl_3, boringssl]
+        crypto: ${{ fromJson(needs.choose_crypto_matrix.outputs.matrix )}}
 
     env:
       CRYPTO_DIR: "./alternatives/${{ matrix.crypto }}"