chore: add workflow to auto-delete branches on PR merge + bulk cleanup

.github/workflows/cleanup-branches.yml

@@ -0,0 +1,120 @@
+name: Cleanup Merged PR Branches
+
+on:
+  # Auto-delete head branch whenever a PR is merged
+  pull_request:
+    types: [closed]
+  # Manual trigger to bulk-delete all existing merged-PR branches
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+jobs:
+  cleanup-on-merge:
+    if: github.event_name == 'pull_request' && github.event.pull_request.merged == true
+    name: Delete branch on PR merge
+    runs-on: ubuntu-latest
+    steps:
+      - name: Delete head branch
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const branch = context.payload.pull_request.head.ref;
+            const owner = context.repo.owner;
+            const repo = context.repo.repo;
+
+            // Never delete protected branches
+            const protectedBranches = ['main', 'develop', 'master'];
+            if (protectedBranches.includes(branch)) {
+              console.log(`Skipping protected branch: ${branch}`);
+              return;
+            }
+
+            try {
+              await github.rest.git.deleteRef({
+                owner,
+                repo,
+                ref: `heads/${branch}`,
+              });
+              console.log(`Deleted branch: ${branch}`);
+            } catch (err) {
+              if (err.status === 422) {
+                console.log(`Branch already deleted: ${branch}`);
+              } else {
+                throw err;
+              }
+            }
+
+  bulk-cleanup:
+    if: github.event_name == 'workflow_dispatch'
+    name: Bulk delete all merged-PR branches
+    runs-on: ubuntu-latest
+    steps:
+      - name: Delete branches for merged PRs
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const owner = context.repo.owner;
+            const repo = context.repo.repo;
+
+            const protectedBranches = new Set(['main', 'develop', 'master']);
+
+            // Collect all head branches from merged PRs (paginate through all pages)
+            const mergedBranches = new Set();
+            for await (const response of github.paginate.iterator(
+              github.rest.pulls.list,
+              { owner, repo, state: 'closed', per_page: 100 }
+            )) {
+              for (const pr of response.data) {
+                if (pr.merged_at) {
+                  mergedBranches.add(pr.head.ref);
+                }
+              }
+            }
+
+            // Fetch all current branches
+            const existingBranches = new Set();
+            for await (const response of github.paginate.iterator(
+              github.rest.repos.listBranches,
+              { owner, repo, per_page: 100 }
+            )) {
+              for (const branch of response.data) {
+                existingBranches.add(branch.name);
+              }
+            }
+
+            // Delete branches that are in merged PRs and still exist
+            const toDelete = [...mergedBranches].filter(
+              b => existingBranches.has(b) && !protectedBranches.has(b)
+            );
+
+            console.log(`Found ${toDelete.length} branches to delete.`);
+            let deleted = 0;
+            let failed = 0;
+
+            for (const branch of toDelete) {
+              try {
+                await github.rest.git.deleteRef({
+                  owner,
+                  repo,
+                  ref: `heads/${branch}`,
+                });
+                console.log(`Deleted: ${branch}`);
+                deleted++;
+              } catch (err) {
+                if (err.status === 422) {
+                  console.log(`Already gone: ${branch}`);
+                } else {
+                  console.error(`Failed to delete ${branch}: ${err.message}`);
+                  failed++;
+                }
+              }
+            }
+
+            console.log(`Done. Deleted: ${deleted}, Failed: ${failed}`);
+            if (failed > 0) {
+              throw new Error(`Failed to delete ${failed} branch(es). See logs above.`);
+            }