ci(auto-merge): restore target-repo input with deprecation note (#191)

* ci(auto-merge): restore `target-repo` input with deprecation note

* ci(auto-merge): refine deprecation message

Author: caugner

.github/workflows/auto-merge.yml

@@ -13,6 +13,11 @@ on:
         default: false
         required: false
         type: boolean
+      target-repo:
+        description: |
+          (Deprecated) This input is deprecated and will be removed soon. Remove it from your workflow, or it will start failing silently. To prevent fork execution, add this to your job instead: if: github.repository_owner == 'your-org'"
+        required: false
+        type: string
     secrets:
       GH_TOKEN:
         description: "Personal access token passed from the caller workflow"
@@ -27,6 +32,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: Warn on deprecated inputs
+        if: inputs.target-repo != ''
+        run: |
+          echo "::warning::The 'target-repo' input is deprecated and will be removed soon. Remove it from your workflow, or it will start failing silently. To prevent fork execution, add this to your job instead: if: github.repository_owner == 'your-org'"
+
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with: