feat: Prevent running on initial commit

Author: chriswblake

.github/workflows/1-first-codespace.yml

@@ -14,7 +14,26 @@ env:
   STEP_2_FILE: ".github/steps/2-custom-image.md"
 
 jobs:
+  stop_if_initial_commit:
+    name: Stop workflow if initial commit
+    runs-on: ubuntu-latest
+    if: |
+      github.event_name == 'push' &&
+      github.ref == 'refs/heads/main' &&
+      startsWith(github.event.head_commit.message, 'Initial commit')
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Cancel workflow if there is only 1 commit in history
+        run: |
+          if [ "$(git rev-list --count HEAD)" -eq 1 ]; then
+            gh run cancel ${{ github.run_id }}
+          fi
+
   find_exercise:
+    needs: [stop_if_initial_commit]
     name: Find Exercise Issue
     uses: skills/exercise-toolkit/.github/workflows/find-exercise-issue.yml@v0.5.0