Merge pull request ampproject#7649 from ampproject/enhancement/workflows

Update `Build, test & measure` workflow

.github/actions/determine-changed-files/action.yml

@@ -0,0 +1,84 @@
+name: Determine count of changed files
+
+description: Determine count of changed files based on the current branch and the base branch
+
+outputs:
+  count:
+    description: The count of changed files
+    value: ${{ steps.determine-file-counts.outputs.count }}
+  php-count:
+    description: The count of changed PHP files
+    value: ${{ steps.determine-file-counts.outputs.php-count }}
+  css-count:
+    description: The count of changed CSS files
+    value: ${{ steps.determine-file-counts.outputs.css-count }}
+  js-count:
+    description: The count of changed JS files
+    value: ${{ steps.determine-file-counts.outputs.js-count }}
+  gha-workflow-count:
+    description: The count of changed GHA workflow files
+    value: ${{ steps.determine-file-counts.outputs.gha-workflow-count }}
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Fetch base branch
+      # Only fetch base ref if it's a PR.
+      if: ${{ github.base_ref != null }}
+      shell: bash
+      run: git fetch --depth=1 --no-tags origin ${{ github.base_ref }}
+
+    - name: Determine modified files for PR
+      if: ${{ github.base_ref != null }}
+      shell: bash
+      run: echo "MODIFIED_FILES=$(git diff --name-only FETCH_HEAD HEAD | base64 -w 0)" >> $GITHUB_ENV
+
+    - name: Determine modified files for commit
+      if: ${{ github.base_ref == null }}
+      shell: bash
+      run: echo "MODIFIED_FILES=$(git diff --name-only HEAD~1 HEAD | base64 -w 0)" >> $GITHUB_ENV
+
+    - name: Determine if modified files should make the workflow run continue
+      id: determine-file-counts
+      shell: bash
+      run: |
+        # Get modified files.
+        MODIFIED_FILES=$(echo "$MODIFIED_FILES" | base64 -d)
+
+        # Determine file counts.
+        FILE_COUNT=$(php -f ./.github/actions/determine-changed-files/determine-modified-files-count.php "$IGNORE_PATH_REGEX" "$MODIFIED_FILES" --invert)
+        PHP_FILE_COUNT=$(php -f ./.github/actions/determine-changed-files/determine-modified-files-count.php ".+\.php|composer\.(json|lock)|phpstan\.neon\.dist" "$MODIFIED_FILES")
+        CSS_FILE_COUNT=$(php -f ./.github/actions/determine-changed-files/determine-modified-files-count.php ".+\.s?css|package\.json|package-lock\.json" "$MODIFIED_FILES")
+        JS_FILE_COUNT=$(php -f ./.github/actions/determine-changed-files/determine-modified-files-count.php ".+\.(js|snap)|package\.json|package-lock\.json" "$MODIFIED_FILES")
+        GHA_WORKFLOW_COUNT=$(php -f ./.github/actions/determine-changed-files/determine-modified-files-count.php "(\.github\/workflows\/.+\.yml)" "$MODIFIED_FILES")
+
+        # Set output variables.
+        echo "count=$FILE_COUNT" >> $GITHUB_OUTPUT
+        echo "php-count=$PHP_FILE_COUNT" >> $GITHUB_OUTPUT
+        echo "css-count=$CSS_FILE_COUNT" >> $GITHUB_OUTPUT
+        echo "js-count=$JS_FILE_COUNT" >> $GITHUB_OUTPUT
+        echo "gha-workflow-count=$GHA_WORKFLOW_COUNT" >> $GITHUB_OUTPUT
+
+        # Add modified files summary.
+        echo "# Modified files summary" >> $GITHUB_STEP_SUMMARY
+        echo "## Modified files" >> $GITHUB_STEP_SUMMARY
+        echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+        echo "$MODIFIED_FILES" >> $GITHUB_STEP_SUMMARY
+        echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+        echo "## Modified files count" >> $GITHUB_STEP_SUMMARY
+        echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+        echo "Total modified files: $FILE_COUNT" >> $GITHUB_STEP_SUMMARY
+        echo "PHP files: $PHP_FILE_COUNT" >> $GITHUB_STEP_SUMMARY
+        echo "CSS files: $CSS_FILE_COUNT" >> $GITHUB_STEP_SUMMARY
+        echo "JS files: $JS_FILE_COUNT" >> $GITHUB_STEP_SUMMARY
+        echo "GHA workflow files: $GHA_WORKFLOW_COUNT" >> $GITHUB_STEP_SUMMARY
+        echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+      env:
+        # Ignore Paths:
+        # - .github/
+        # - !.github/actions
+        # - !.github/workflows
+        # - .github/actions/draft-release/
+        # - .wordpress-org/
+        # - docs/
+        IGNORE_PATH_REGEX: \.github\/(?!actions|workflows)|\.wordpress-org\/|docs\/|\.github\/actions\/draft-release\/