Oh Merge

oh-merge

Holistically review pending GitHub issue PRs from oh-task, then squash-merge them as a cohesive batch.

Invocation

/oh-merge

Flow

1. Load project background from AGENTS.md, relevant .oh/ artifacts, and RNA MCP context when available.

2. Find all PRs with oh-merge label:

   gh pr list --label oh-merge --json number,title,headRefName,baseRefName,additions,deletions
   

   Only PRs with the oh-merge label are eligible for merge.

   IMPORTANT: PRs with merge conflicts ARE eligible. The skill rebases and resolves conflicts in step 6. Do NOT skip PRs because of conflict status - that's exactly what this skill handles.

3. Build dependency graph and identify stacks:

   • Create adjacency list: baseRefName → [PRs targeting it]

   • Find root PRs: those where baseRefName = main (or master)

   • Identify stacks: chains where child PRs target parent PR branches

   • Detect cycles: If a branch eventually targets itself, report error and skip

   • Example graph:

     main ← PR #42 (issue/123) ← PR #43 (issue/456)
     main ← PR #44 (issue/789)  [separate stack]
     

4. Select stack to process:

   • If multiple independent stacks exist, pick first by lowest root PR number (FIFO by age)
   • If multiple PRs target the same base branch, order by PR number (lowest first)
   • Report other stacks as "queued for next run"
   • Process only one stack per invocation to keep merges atomic
   • Orphaned children: If a child PR targets a branch that doesn't exist (parent merged externally), update its base to main and treat as a root

5. Batch review - evaluate all PRs in the selected stack together:

   • Collect combined diff of all PRs against main
   • Run the repo-local /review skill on the combined changes
   • Evaluate:
     • Do changes conflict logically? (same code modified differently)
     • Is there duplicate work? (two PRs solving same problem)
     • Do changes compose well? (feature A + feature B = coherent whole)
     • Any cross-cutting concerns? (shared dependencies, API changes)
   • If concerns found:
     • Report issues
     • Ask human whether to proceed or address first

   This batch review supplements, but never replaces, each PR's project-specific /ship gate.

6. Merge stack in dependency order (root first, then children):

   For each PR in the stack, starting from the root:

   1. Rewrite the branch onto its final target first:
      • Fetch, check out, and rebase onto the current target branch.
      • Resolve conflicts, run repo-local /review, and force-push with lease.
      • For a child whose parent has merged, retarget it to main, rebase, and force-push before any validation.
      • Any later rewrite or retarget invalidates all prior ship, independent final-diff approval, and CI evidence.

   a. Verify the full RNA ship gate completed on the final pushed commit:

   • The PR is ready for review, not draft.
   • Required /ship step comments are present, including RNA-grounded review, independent review, regression oracle, merit assessment, manual verification, delivery verification, and final comment sweep.
   • The final acceptance-criteria gate passed.
   • A fresh, separate repo-local /review sub-agent posted explicit APPROVE for the exact final commit.
   • CodeRabbit is optional supplemental feedback: never trigger or wait for it, but all actionable comments already present are addressed. If any evidence is missing, stop and run /ship <pr-number>; do not merge directly.

   b. Verify CI is passing on that same final commit:

   gh pr checks <pr-number> --fail-on-error
   

   If CI is failing, stop and report error.

   c. Squash merge:

   gh pr merge <pr-number> --squash
   

   d. For child PRs in the stack (after parent merged):

   • Update base branch to main:

     gh pr edit <child-pr-number> --base main
     

   • Rebase child onto main:

     gh pr checkout <child-pr-number>
     git rebase origin/main
     git push --force-with-lease
     

   • The rewrite invalidates prior validation. Return to step 0 and rerun the full ship gate, fresh independent final-diff review, and CI before merging.

   e. On merge failure - If any PR in the stack fails to merge:

   • Stop processing the stack
   • Report which PRs were merged successfully and which failed
   • Signal error: already-merged PRs stay merged, failed PR remains open
   • Next oh-merge run will see the failed PR as a new root (its parent is now in main)

   Note: GitHub automatically closes linked issues when the PR merges through Closes #N in the PR body.

Stacked PRs

When PRs target other PR branches (not main), oh-merge detects the stack and processes it:

Detection:

gh pr list --label oh-merge --json number,title,headRefName,baseRefName

• PRs with baseRefName = main are roots
• PRs with baseRefName = issue/<number> are children targeting that parent
• Ignore merge conflict status - we handle conflicts during rebase

Graph building:

adjacency[baseRefName] = [list of PRs targeting it]

Example:
  adjacency["main"] = [PR #42, PR #44]
  adjacency["issue/123"] = [PR #43]

Stack 1: main ← #42 (issue/123) ← #43 (issue/456)
Stack 2: main ← #44 (issue/789)

Merge sequence (for Stack 1):

1. Merge #42 to main
2. Update #43: gh pr edit 43 --base main
3. Rebase #43 onto main: git rebase origin/main && git push --force-with-lease
4. Merge #43 to main

After processing:

Before:  PR #43 → issue/123 → main
         PR #42 → main
         PR #44 → main (separate stack)

After:   PR #42 merged to main (issue #123 auto-closed)
         PR #43 rebased onto main, merged to main (issue #456 auto-closed)
         PR #44 remains for next oh-merge run

Batch Review Criteria

The holistic review checks what individual PR reviews can't:

• Logical conflicts: PR A assumes X, PR B assumes not-X
• Duplication: Both PRs add similar functionality
• Integration issues: Combined changes break something neither breaks alone
• Ordering dependencies: PR B depends on PR A being merged first (auto-detected for stacked PRs)
• Scope creep: Batch as a whole does more than originally intended

Prerequisites

• PRs must have the oh-merge label (human approval gate)
• Each PR must have completed the repository-specific /ship pipeline
• PRs must be ready for review, not draft
• Every PR must have an explicit APPROVE from a fresh, separate repo-local /review sub-agent on the exact final commit
• Any later diff change invalidates that approval and requires a new fresh reviewer
• CodeRabbit is optional supplemental feedback: never trigger or wait for it, but address actionable comments already present
• PRs must have CI passing
• PRs should have "Closes #N" in body for auto-close (created by oh-task)
• Batch review must pass (or human override)

Note: The oh-merge label must be created in the repo. This is opt-in per repo.

Exit Conditions

• Success: Selected stack fully merged
• Partial success: Some PRs in stack merged, then failure
• Needs attention: Batch review raised concerns - waiting for human decision
• Error: Unrecoverable failure (code conflicts, CI failing, cycle detected)
• No work: No PRs with oh-merge label found

Completion Signaling (MANDATORY)

CRITICAL: You MUST signal completion when done. Call the signal_completion tool as your FINAL action.

Signal based on outcome:

If you do not signal, the orchestrator will not know you are done and the session becomes orphaned.

Fallback: If the signal_completion tool is not available, output your completion status as your final message in the format: COMPLETION: status=<status> message=<message> or COMPLETION: status=<status> error=<reason>.

Example

Basic (no stacks)

$ /oh-merge

Finding PRs with oh-merge label...
Found 2 PRs:
  PR #42 "Fix validation bug" (issue/123) → main (CI ✓)
  PR #44 "Refactor validator" (issue/789) → main (CI ✓)

Building dependency graph...
  Stack 1: main ← #42
  Stack 2: main ← #44
  2 independent stacks, processing Stack 1

Running batch review on Stack 1 (1 PR)...
Batch review complete: ✓ No issues

Processing PR #42 (Fix validation bug)...
  Verifying CI... ✓
  Rebasing onto main... clean
  Squash merging... ✓
  Issue #123 will auto-close on merge

Merge complete.
  Merged: 1 PR (#42)
  Remaining: 1 PR (#44 - queued for next run)

signal_completion(status: "success", message: "Merged 1 PR (#42)")
Done.

Stacked PRs

$ /oh-merge

Finding PRs with oh-merge label...
Found 3 PRs:
  PR #42 "Fix validation bug" (issue/123) → main (CI ✓)
  PR #43 "Add edge case tests" (issue/456) → issue/123 (CI ✓)
  PR #44 "Refactor validator" (issue/789) → main (CI ✓)

Building dependency graph...
  Stack 1: main ← #42 (issue/123) ← #43 (issue/456)
  Stack 2: main ← #44
  2 stacks found, processing Stack 1 (2 PRs)

Running batch review on Stack 1...
Collecting diffs: +547 -103 across 8 files
Batch review complete: ✓ No issues

Processing stack root: PR #42 (Fix validation bug)...
  Verifying CI... ✓
  Rebasing onto main... clean
  Squash merging... ✓
  Issue #123 will auto-close on merge

Processing stack child: PR #43 (Add edge case tests)...
  Verifying CI... ✓
  Updating base branch to main... done
  Rebasing onto main... clean
  Squash merging... ✓
  Issue #456 will auto-close on merge

Stack merged.
  Merged: 2 PRs (#42, #43)
  Remaining: 1 PR (#44 - queued for next run)

signal_completion(status: "success", message: "Merged 2 PRs (#42, #43)")
Done.