update validation ci accept pr number as input to run against

Author: c1ly

.github/workflows/rust-validation-tests.yml

@@ -15,6 +15,16 @@ permissions:
 
 on:
   workflow_dispatch:
+    inputs:
+      pr_number:
+        description: "Pull request number to run validation tests against"
+        required: true
+        type: number
+
+# Cancel in-progress runs for the same PR if a new manual run is started
+concurrency:
+  group: ${{ github.workflow }}-${{ inputs.pr_number }}
+  cancel-in-progress: true
 
 env:
   CARGO_TERM_COLOR: always
@@ -23,9 +33,12 @@ jobs:
   validation_tests:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Checkout PR merge ref
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
+          ref: refs/pull/${{ inputs.pr_number }}/merge
           submodules: true
+          fetch-depth: 0
       - uses: arduino/setup-protoc@c65c819552d16ad3c9b72d9dfd5ba5237b9c906b # v3.0.0
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}