run core tests only if core files are modified (#1275)

According to
https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#example-including-paths
> When all the path names match patterns in paths-ignore, the workflow
will not run.
> If any path names do not match patterns in paths-ignore, even if some
path names match the patterns, the workflow will run.

Author: tianyu-l

.github/workflows/integration_test_8gpu.yaml

@@ -3,10 +3,15 @@ name: 8 GPU Integration Test
 on:
   push:
     branches: [ main ]
+    paths-ignore:
+      - 'torchtitan/experiments/**'
   pull_request:
+    paths-ignore:
+      - 'torchtitan/experiments/**'
   schedule:
     # Runs every 6 hours
     - cron: '0 */6 * * *'
+
 concurrency:
   group: unit-test${{ github.workflow }}-${{ github.ref == 'refs/heads/main' && github.run_number || github.ref }}
   cancel-in-progress: true

.github/workflows/integration_test_8gpu_h100.yaml

@@ -1,12 +1,17 @@
-name: 8 GPU Integration Test at H100
+name: 8 GPU Integration Test on H100
 
 on:
   push:
     branches: [ main ]
+    paths-ignore:
+      - 'torchtitan/experiments/**'
   pull_request:
+    paths-ignore:
+      - 'torchtitan/experiments/**'
   schedule:
     # Runs every 6 hours
     - cron: '0 */6 * * *'
+
 concurrency:
   group: unit-test${{ github.workflow }}-${{ github.ref == 'refs/heads/main' && github.run_number || github.ref }}
   cancel-in-progress: true

.github/workflows/unit_test_cpu.yaml

@@ -3,7 +3,11 @@ name: CPU Unit Test
 on:
   push:
     branches: [ main ]
+    paths-ignore:
+      - 'torchtitan/experiments/**'
   pull_request:
+    paths-ignore:
+      - 'torchtitan/experiments/**'
 
 concurrency:
   group: unit-test${{ github.workflow }}-${{ github.ref == 'refs/heads/main' && github.run_number || github.ref }}