Run github actions in the correct context and compare main vs PR

.github/workflows/benchmark.yml

@@ -1,20 +1,70 @@
 name: Benchmarks
 on:
-  pull_request_target:
+  pull_request:
     branches:
       - main
 
+permissions:
+  issues: write
+
 jobs:
   benchmark:
     name: Run benchmarks
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - name: Checkout main branch
+        uses: actions/checkout@v2
+        with:
+          ref: main
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
-      - run: echo \`\`\` > results.txt && cargo bench -- solvers --exact | tail -n +6  >> results.txt && echo \`\`\` >> results.txt
-      - uses: thollander/actions-comment-pull-request@v2
+
+      - name: Run benchmarks on main - solvers
+        run: cargo bench -- solvers --exact | tail -n +6  > results_main.txt
+
+      - name: Checkout PR branch
+        uses: actions/checkout@v2
+
+      - name: Run benchmarks on PR branch
+        run: cargo bench -- solvers --exact | tail -n +6 > results_pr.txt
+
+      - name: Find Comment
+        uses: peter-evans/find-comment@v3
+        id: fc
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          comment-author: 'github-actions[bot]'
+          body-includes: Benchmark Results - Solvers
+
+      - name: Create or update comment
+        uses: actions/github-script@v7
         with:
-          filepath: results.txt
-          comment_tag: "Benchmark Results"
+          script: |
+            const fs = require('fs');
+            const issue_number = context.issue.number;
+            const comment_id = '${{ steps.fc.outputs.comment-id }}';
+            let results_main = 'Benchmarks did not run successfully on main.';
+            let results_pr = 'Benchmarks did not run successfully on PR.';
+            if (fs.existsSync('results_main.txt')) {
+              results_main = fs.readFileSync('results_main.txt', 'utf8');
+            }
+            if (fs.existsSync('results_pr.txt')) {
+              results_pr = fs.readFileSync('results_pr.txt', 'utf8');
+            }
+            const body = `Benchmark Results - Solvers\n\n<details><summary>Main</summary>\n\n\`\`\`\n${results_main}\n\`\`\`\n</details>\n<details><summary>PR</summary>\n\n\`\`\`\n${results_pr}\n\`\`\`\n</details>`;
+            if (comment_id) {
+              github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: comment_id,
+                body: body,
+              });
+            } else {
+              github.rest.issues.createComment({
+                issue_number: issue_number,
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                body: body,
+              });
+            }