chore(ci): run benchmarks on base branch first

.github/workflows/bench-branch.yml

@@ -1,16 +1,38 @@
 on:
   push:
-    branches-ignore:
-      - "dependabot/**"
+    branches:
+      - "master"
     tags:
       - "*"
+  pull_request:
 name: benchmark
 jobs:
   runBenchmark:
     name: run benchmark
     runs-on: ubuntu-latest
+    if: "!startsWith(github.head_ref, 'dependabot/')"
     steps:
-      - uses: actions/checkout@v3
+      - name: Check out base
+        if: github.event_name == 'pull_request'
+        uses: actions/checkout@v3
+        with:
+          ssh-key: ${{secrets.API_KEY}}
+          repo: ${{github.event.pull_request.base.repo.full_name}}
+          ref: ${{github.event.pull_request.base.ref}}
+      - name: Run benchmarks on base for comparison
+        if: github.event_name == 'pull_request'
+        run: cargo bench --features internal-bench
+
+      - name: Check out head
+        uses: actions/checkout@v3
+        if: github.event_name == 'pull_request'
+        with:
+          ssh-key: ${{secrets.API_KEY}}
+          repo: ${{github.event.pull_request.head.repo.full_name}}
+          ref: ${{github.event.pull_request.head.ref}}
+      - name: Check out head
+        uses: actions/checkout@v3
+        if: github.event_name == 'push'
         with:
           ssh-key: ${{secrets.API_KEY}}