Merge remote-tracking branch 'origin/next' into merge-train/barretenberg

Author: ludamad

.github/workflows/ci3.yml

@@ -34,6 +34,9 @@ jobs:
         with:
           # The commit to checkout. We want our actual commit, and not the result of merging the PR to the target.
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
+          # Fetch PR commits depth (we'll deepen by 1 in squash script if needed)
+          fetch-depth: ${{ github.event.pull_request.commits || 0 }}
+          token: ${{ secrets.AZTEC_BOT_GITHUB_TOKEN }}
 
       - name: CI Merge Queue Override (grind on PR)
         if: contains(github.event.pull_request.labels.*.name, 'ci-merge-queue')
@@ -98,10 +101,21 @@ jobs:
           echo "$GCP_SA_KEY" | base64 -w 0 > gcp_sa_key.b64
           echo "GCP_SA_KEY_B64=$(cat gcp_sa_key.b64)" >> $GITHUB_ENV
 
+      - name: Get Tree Hash
+        run: echo "TREE_HASH=$(git rev-parse HEAD^{tree})" >> $GITHUB_ENV
+
+      - name: Check CI Cache
+        id: ci_cache
+        uses: actions/cache@v3
+        with:
+          path: ci-success.txt
+          key: ci-${{ github.event_name == 'merge_group' && 'merge-queue' || env.CI_FULL == '1' && 'full' || env.CI_DOCS == '1' && 'docs' || env.CI_BARRETENBERG == '1' && 'barretenberg' || 'fast' }}-${{ env.TREE_HASH }}
+
       #############
       # Run
       #############
       - name: Run
+        if: steps.ci_cache.outputs.cache-hit != 'true'
         env:
           AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
           AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
@@ -136,6 +150,26 @@ jobs:
             exec ./ci.sh fast
           fi
 
+      - name: Save CI Success
+        if: steps.ci_cache.outputs.cache-hit != 'true'
+        run: echo "success" > ci-success.txt
+
+      # If we have passed CI and labelled with ci-squash-and-merge, squash the PR.
+      # This will rerun CI on the squash commit - but is intended to be a no-op due to caching.
+      - name: CI Squash and Merge
+        if: contains(github.event.pull_request.labels.*.name, 'ci-squash-and-merge')
+        env:
+          GITHUB_TOKEN: ${{ secrets.AZTEC_BOT_GITHUB_TOKEN }}
+        run: |
+          # Get the base commit (merge-base) for the PR
+          ./scripts/merge-train/squash-pr.sh \
+            "${{ github.event.pull_request.number }}" \
+            "${{ github.event.pull_request.head.ref }}" \
+            "${{ github.event.pull_request.base.ref }}" \
+            "${{ github.event.pull_request.base.sha }}"
+          gh pr edit "${{ github.event.pull_request.number }}" --remove-label "ci-squash-and-merge"
+          gh pr ready "${{ github.event.pull_request.number }}" || true
+
       - name: Download benchmarks
         if: github.event_name == 'merge_group'
         run: ./ci.sh gh-bench
@@ -155,39 +189,3 @@ jobs:
           comment-on-alert: false
           fail-on-alert: false
           max-items-in-chart: 100
-
-  notify:
-    runs-on: ubuntu-latest
-    if: github.event_name == 'push' && failure()
-    needs:
-      - ci
-    steps:
-      - name: Checkout Code
-        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
-
-      - name: Get Context
-        id: get_context
-        run: |
-          authors=$(git log -1 --pretty=format:'%an <%ae>')
-          echo "authors=${authors}" >> $GITHUB_OUTPUT
-          # Note, we have to make sure double quotes don't break our JSON.
-          title=$(git log -1 --pretty=format:'%s' | sed s/\"/\'/g)
-          echo "commit_title=${title}" >> $GITHUB_OUTPUT
-          failed_jobs=""
-          [ "${{ needs.ci-grind.result }}" = "failure" ] && failed_jobs+="ci-grind"
-          [ "${{ needs.ci.result }}" = "failure" ] && failed_jobs+="ci"
-          echo "failed_jobs=${failed_jobs}" >> $GITHUB_OUTPUT
-          cat $GITHUB_OUTPUT
-
-      - name: Send Notification
-        uses: slackapi/slack-github-action@6c661ce58804a1a20f6dc5fbee7f0381b469e001
-        with:
-          payload: |
-            {
-              "text": "Failure on ${{ github.ref_name }}\nCommit: ${{ steps.get_context.outputs.commit_title }}",
-              "url": "https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}",
-              "authors": "${{ steps.get_context.outputs.authors }}",
-              "failed_jobs": "${{ steps.get_context.outputs.failed_jobs }}"
-            }
-        env:
-          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_NOTIFY_WORKFLOW_TRIGGER_URL2 }}

.github/workflows/merge-train-create-pr.yml

@@ -0,0 +1,42 @@
+name: Merge-Train Create PR
+
+on:
+  push:
+    branches:
+      - 'merge-train/*'
+
+jobs:
+  create-pr:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+    
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      
+      - name: Check if PR exists and create if needed
+        env:
+          GITHUB_TOKEN: ${{ secrets.AZTEC_BOT_GITHUB_TOKEN }}
+        run: |
+          branch="${{ github.ref_name }}"
+          
+          # Check if PR already exists for this branch
+          existing_pr=$(gh pr list --state open --head "$branch" --json number --jq '.[0].number // empty')
+          
+          if [[ -z "$existing_pr" ]]; then
+            echo "No PR exists for $branch, creating one"
+            
+            # Determine base branch (default to next)
+            base_branch="next"
+            
+            # Create PR with ci-no-squash label
+            gh pr create --base "$base_branch" --head "$branch" \
+              --title "feat: $branch" \
+              --body "$(echo -e "See [merge-train-readme.md](https://github.com/${{ github.repository }}/blob/next/.github/workflows/merge-train-readme.md).\nThis is a merge-train.")" \
+              --label "ci-no-squash"
+            
+            echo "Created PR for $branch"
+          else
+            echo "PR #$existing_pr already exists for $branch"
+          fi

.github/workflows/merge-train-readme.md

@@ -29,10 +29,10 @@ Inspired by [rust rollups](https://forge.rust-lang.org/release/rollups.html), bu
 
 ### Merge Train Lifecycle
 
-1. **Creation**: A merge train PR is created with an empty commit. All existing PRs are updated to prevent issues due to the squash merge.
-2. **Accumulation**: Feature PRs are merged into the merge train branch
-3. **Auto-merge**: After 4 hours of inactivity (with meaningful commits), the train is automatically merged
-4. **Recreation**: The cycle starts again with a new empty merge train
+1. **Creation**: A merge train PR is created automatically when changes are pushed to the branch and labeled with `ci-no-squash`.
+2. **Accumulation**: Feature PRs are merged into the merge train branch, squashed
+3. **Auto-merge**: After 4 hours of inactivity (with meaningful commits), the train is automatically merged with a merge-commit (not a squash)
+4. **Recreation**: The cycle starts again with a new merge train
 
 ## Handling Merge Failures
 
@@ -47,31 +47,3 @@ When a merge-train fails due to issues from `next`:
 - Merge a revert or workaround into `next`
 - The fix will auto-propagate to merge-train via automation
 - Best when key assumptions are broken or multiple trains affected
-
-## Resolving Merge Conflicts
-
-When merge conflicts arise in the merge-train branch:
-
-1. Pull the latest merge-train branch locally
-2. Resolve conflicts in your editor
-3. Push the merge commit directly to the merge-train branch
-
-**Note**: Keep the merge commit when resolving conflicts - squashing won't help with the history divergence issues that occur after merge-train recreation.
-
-## RECOVERING FROM MERGE TRAIN RECREATION
-
-When a merge-train is recreated after squashing, PRs with commits from the old merge-train need rebasing.
-
-### Three Recovery Options:
-
-1. **Automatic (Recommended)**: Add the `auto-rebase` label to your PR
-2. **Script**: Run `./scripts/auto_rebase_pr.sh` locally
-3. **Manual**: Follow the git instructions posted as a comment on your PR
-
-The automation will detect if your PR contains commits from the old merge-train and post specific rebase instructions as a comment. These instructions use `git rebase --onto` to cleanly move your commits to the new base, preserving your work while avoiding the squashed history.
-
-**Important**: 
-- PRs without commits from the old merge-train need no action
-- The recreation process automatically checks each PR and only comments on affected ones
-- The posted git commands help you merge the old PR head and then rebase onto the new base
-- Always check your diff afterwards for unexpected changes

.github/workflows/merge-train-recreate.yml

@@ -3,18 +3,7 @@ name: Merge-Train Recreate
 on:
   pull_request:
     types: [closed]
-  workflow_dispatch:
-    inputs:
-      merge_train_branch:
-        description: 'Merge train branch to recreate (e.g., merge-train/docs)'
-        required: true
-        type: string
-      base_branch:
-        description: 'Base branch (e.g., next)'
-        required: true
-        type: string
-        default: 'next'
-
+≈
 jobs:
   recreate:
     if: ${{ github.event_name == 'workflow_dispatch' || (github.event.pull_request.merged && startsWith(github.event.pull_request.head.ref, 'merge-train/')) }}
@@ -36,24 +25,14 @@ jobs:
 
       - name: Recreate branch
         run: |
-          # Determine branch names based on event type
-          if [[ "${{ github.event_name }}" == "workflow_dispatch" ]]; then
-            MERGE_TRAIN_BRANCH="${{ github.event.inputs.merge_train_branch }}"
-            BASE_BRANCH="${{ github.event.inputs.base_branch }}"
-            # For manual dispatch, use current SHA and get latest from base branch
-            HEAD_COMMIT_SHA="${{ github.sha }}"
-            BASE_COMMIT_SHA=$(git rev-parse origin/$BASE_BRANCH)
-          else
-            MERGE_TRAIN_BRANCH="${{ github.event.pull_request.head.ref }}"
-            BASE_BRANCH="${{ github.event.pull_request.base.ref }}"
-            HEAD_COMMIT_SHA="${{ github.event.pull_request.head.sha }}"
-            BASE_COMMIT_SHA="${{ github.event.pull_request.merge_commit_sha }}"
-          fi
+          MERGE_TRAIN_BRANCH="${{ github.event.pull_request.head.ref }}"
+          BASE_BRANCH="${{ github.event.pull_request.base.ref }}"
+          git fetch origin "$BASE_BRANCH"
+          git checkout -b "$MERGE_TRAIN_BRANCH" "origin/$BASE_BRANCH"
+
+      - name: Push branch
+        continue-on-error: true
+        run: |
+          # This will generally only succeed if the branch does not exist, as a fallback if the branch is unprotected and gets deleted.
+          git push origin "$MERGE_TRAIN_BRANCH"
 
-          # Use aztecbot token for all operations including PR creation
-          GH_TOKEN=${{ secrets.AZTEC_BOT_GITHUB_TOKEN }} \
-          ./scripts/merge-train/recreate-branch.sh \
-            "$MERGE_TRAIN_BRANCH" \
-            "$BASE_BRANCH" \
-            "$BASE_COMMIT_SHA" \
-            "$HEAD_COMMIT_SHA"

.github/workflows/squashed-pr-check.yml

@@ -0,0 +1,28 @@
+name: Squashed PR Check
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, labeled, unlabeled]
+
+jobs:
+  check-squashed:
+    runs-on: ubuntu-latest
+    # Only run if PR doesn't have ci-no-squash label AND is targeting 'next' branch
+    if: ${{ !contains(github.event.pull_request.labels.*.name, 'ci-no-squash') && github.event.pull_request.base.ref == 'next' }}
+    
+    steps:
+      - name: Check if PR is squashed
+        run: |
+          # Get number of commits from the event payload
+          commit_count=${{ github.event.pull_request.commits }}
+          
+          echo "PR has $commit_count commits"
+          
+          # Fail if PR has more than 1 commit
+          if [ "$commit_count" -gt 1 ]; then
+            echo "::error::This PR has $commit_count commits but must be squashed to a single commit."
+            echo "::error::Either squash your commits or add the 'ci-no-squash' label if multiple commits are intentional."
+            exit 1
+          fi
+          
+          echo "✅ PR is properly squashed with $commit_count commit"

CI.md

@@ -256,6 +256,43 @@ ci rlog
 
 This will also show the last completed log if the run has already completed. You can provide a GA run id (output by `ci trigger`) to see a historical run.
 
+## CI Labels and Automation
+
+### Pull Request Labels
+
+The following labels can be used to control CI behavior on pull requests:
+
+- **`ci-squash-and-merge`**: Automatically squashes all commits in your PR into a single commit. Add this label to trigger squashing. The label is automatically removed after squashing. Thanks to content-based caching (see below), subsequent CI runs will be skipped if the content hasn't changed.
+
+- **`ci-no-squash`**: Exempts the PR from the single-commit requirement. Use when multiple commits are intentional (e.g., merge-train PRs).
+
+- **`ci-merge-queue`**: Simulates merge queue behavior on your PR, running the full test suite.
+
+- **`ci-full`**: Forces a full CI run instead of the default fast run.
+
+- **`ci-docs`**: Runs only documentation-related CI checks.
+
+- **`ci-barretenberg`**: Runs only Barretenberg-related CI checks.
+
+- **`ci-no-cache`**: Disables build caching for this CI run.
+
+- **`ci-no-fail-fast`**: Continues running all tests even if some fail.
+
+### Squash Enforcement
+
+PRs targeting `next` must be squashed to a single commit unless labeled with `ci-no-squash`. PRs targeting other branches (like `merge-train/*`) are automatically exempt from this requirement.
+
+### Top-level Content-Based CI Caching
+
+CI3 has granular caching, but as well it includes an additional layer of caching based on git content. When CI completes successfully, it stores a success marker keyed by the hash of the repository's file tree. On subsequent runs, if the exact same content is detected (same tree hash), CI will skip execution entirely.
+
+This is particularly useful when:
+- You squash commits using `ci-squash-and-merge` - the resulting single commit has the same content, so CI won't re-run
+- You rebase without changes - if the final content is identical, CI is skipped
+- Multiple PRs have identical changes - only the first needs to run CI
+
+The content hash is computed using `git rev-parse HEAD^{tree}`, which provides a unique identifier for the entire file tree state, regardless of commit history.
+
 ## Denoise Logs
 
 When a CI run is taking place and it has a redis cache available, you will see logs like this:

ci.sh

@@ -78,26 +78,45 @@ function prep_vars {
   export DENOISE_WIDTH=32
 }
 
+# We want to run CI with caching - even though it internally uses caching - to quickly catch no-ops that have the same
+# git contents.
+function run_ci_with_cache {
+  local ci_mode=$1
+  local job_id=$2
+  local bootstrap_cmd=$3
+
+  # Check if CI already succeeded for this content
+  local content_hash=$(git rev-parse HEAD^{tree} | cut -c1-16)
+  local cache_key="ci-success-${ci_mode}-${content_hash}.txt"
+
+  if cache_download "$cache_key" 2>/dev/null; then
+    if [ -f "$cache_key" ] && grep -q "success" "$cache_key"; then
+      echo "Found cached success for ${ci_mode} mode with hash $content_hash"
+      exit 0
+    fi
+  fi
+
+  # Spin up ec2 instance and run the CI flow
+  export JOB_ID="$job_id"
+  bootstrap_ec2 "$bootstrap_cmd"
+
+  # Upload success marker
+  echo "success" > success.txt
+  cache_upload "$cache_key" success.txt
+}
+
 case "$cmd" in
   "fast")
-    # Spin up ec2 instance and run the fast flow.
-    export JOB_ID="x1-fast"
-    exec bootstrap_ec2 "./bootstrap.sh ci-fast"
+    run_ci_with_cache "fast" "x1-fast" "./bootstrap.sh ci-fast"
     ;;
   "full")
-    # Spin up ec2 instance and run the full flow.
-    export JOB_ID="x1-full"
-    exec bootstrap_ec2 "./bootstrap.sh ci-full"
+    run_ci_with_cache "full" "x1-full" "./bootstrap.sh ci-full"
     ;;
   "docs")
-    # Spin up ec2 instance and run docs-only CI.
-    export JOB_ID="x1-docs"
-    exec bootstrap_ec2 "./bootstrap.sh ci-docs"
+    run_ci_with_cache "docs" "x1-docs" "./bootstrap.sh ci-docs"
     ;;
   "barretenberg")
-    # Spin up ec2 instance and run barretenberg-only CI.
-    export JOB_ID="x1-barretenberg"
-    exec bootstrap_ec2 "./bootstrap.sh ci-barretenberg"
+    run_ci_with_cache "barretenberg" "x1-barretenberg" "./bootstrap.sh ci-barretenberg"
     ;;
   "grind")
     # Spin up ec2 instance and run the merge-queue flow.