[Repo Assist] Batch open-PR fetch in submit: N API calls → 1 - #12

🤖 This is an automated pull request from Repo Assist, an AI assistant.

Summary

gh stack submit called FindPRForBranch once per active branch to check whether a PR already exists — an N sequential GraphQL round-trips for an N-branch stack.

This PR adds FindOpenPRsForBranches that sends a single batched GraphQL query using field aliases (one aliased pullRequests per branch, filtered to OPEN state), then pre-fetches all results before the submit loop.

Impact

All gh stack submit runs benefit.

How it works

FindOpenPRsForBranches constructs a raw GraphQL query:

{
  repository(owner: "owner", name: "repo") {
    b0: pullRequests(headRefName: "feat/01", states: [OPEN], first: 1) { nodes { id number ... } }
    b1: pullRequests(headRefName: "feat/02", states: [OPEN], first: 1) { nodes { id number ... } }
  }
}

This uses gql.Do(rawQuery, nil, &resp) to send a raw query string, bypassing the struct-based query builder which doesn't support dynamic aliases. Results are distributed back to a map[branch]→*PullRequest.

Graceful fallback

If FindOpenPRsForBranches returns an error (e.g. API version mismatch), submit falls back to the original per-branch FindPRForBranch calls — no user-visible degradation, just slower.

Changes

• internal/github/github.go: New FindOpenPRsForBranches([]string) (map[string]*PullRequest, error) using gql.Do with dynamically-constructed aliased query (OPEN state filter)
• internal/github/client_interface.go: Added FindOpenPRsForBranches to ClientOps interface
• internal/github/mock_client.go: Added FindOpenPRsForBranchesFn; default returns nil, nil to trigger graceful fallback to FindPRForBranch in existing tests
• cmd/submit.go: Pre-fetch with FindOpenPRsForBranches, fall back gracefully on error
• cmd/submit_test.go: TestSubmit_BatchFetchesOpenPRs (verifies batch is called once, per-branch not called); TestSubmit_BatchFetchFallback (verifies fallback works on error)

Relationship to PR #7

PR #7 adds a similar batch optimization for syncStackPRs (fetching any-state PRs). This PR is independent — it targets the submit PR-lookup path (open PRs only) and can be reviewed and merged separately.

Test Status

Tests could not be run in this environment because the Go toolchain requires network access to proxy.golang.org / sum.golang.org (blocked by firewall). The CI workflow will run the full test suite. The fallback path (openPRs == nil → FindPRForBranch) ensures existing tests continue to work without modification.

Generated by 🌈 Repo Assist, see workflow run. Learn more.

Generated by 🌈 Repo Assist, see workflow run. Learn more.

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@11c9a2c442e519ff2b427bf58679f5a525353f76