Run TLAi and upload SARIF report iff git commit contains TLA files

[Build]

.github/workflows/tlaplus.yml

@@ -128,22 +128,28 @@ jobs:
           ## All history for git diff below to succeed.
           fetch-depth: 0
 
+      - name: Check if HEAD commit contains TLA changes.
+        id: git_commit
+        run: echo "::set-output name=contains_tla::$(git diff --name-only HEAD^ | grep -q '\.tla' && echo 'true' || echo 'false')"
+
       - name: Setup NodeJS
+        if: step.git_commit.outputs.contains_tla == 'true'
         ## https://github.com/actions/setup-node
         uses: actions/setup-node@v4
         with:
           node-version: "20"
 
       - name: Run GenAIscript on the TLA+ specs that are added in this pull request.
+        if: step.git_commit.outputs.contains_tla == 'true'
         ## Identify git diff: $(git diff --name-only HEAD^ | grep '.tla')
         ## Install genaiscript runtime: https://microsoft.github.io/genaiscript/reference/cli/
         ## Output LLM response in SARIF format: https://microsoft.github.io/genaiscript/reference/scripts/annotations/ (redirect other output to /dev/null for GH not to also show the annotations)
-        run: npx --yes genaiscript run scripts/TLAi-linter.genai.js $(git diff --name-only HEAD^ | grep '.tla') --max-tokens 2000 --out-annotations results.sarif > /dev/null
+        run: npx --yes genaiscript run scripts/TLAi-linter.genai.js $(git diff --name-only HEAD^ | grep '\.tla') --max-tokens 2000 --out-annotations results.sarif > /dev/null
 
       - name: Upload SARIF file
+        if: (success() || failure()) && step.git_commit.outputs.contains_tla == 'true'
         ## https://sarifweb.azurewebsites.net
         ## https://docs.github.com/en/code-security/code-scanning/integrating-with-code-scanning/uploading-a-sarif-file-to-github
-        if: success() || failure()
         uses: github/codeql-action/upload-sarif@v3
         with:
           sarif_file: results.sarif