One-PR stack: submit reports success, but merge says the stack was not submitted

从 cmd/submit.go 开始，阅读 syncStack 及其调用方，然后对比 cmd/merge.go 中的 remote-stack 检查。使用 issue 中的命令重现 one-PR 流程；完成的标准是 submit 准确报告缺失的 remote-stack，且 merge 给出可用的结果或下一条命令，而不是要求用户重复一次已成功的提交。

Summary

A local stack can contain one branch and one pull request. gh stack submit reports success for this stack:

✓ Pushed and synced 1 branches

However, GitHub does not create a remote stack object. A remote stack requires at least two pull requests.

gh stack merge then rejects the local stack:

✗ this stack has not been submitted to GitHub yet; run `gh stack submit` first

A second gh stack submit does not fix the problem. It reports success again.

Reproduction

1. Create a branch from the trunk branch.
2. Commit a change on the new branch.
3. Initialize a local stack that contains only the new branch.
4. Run gh stack submit and create the pull request.
5. Run gh stack submit again.
6. Run gh stack merge --squash.

Example output:

$ gh stack submit
Checking stack state...
Pushing to origin...
PR #30 for close-clinkr-cli-entry-point is up to date
✓ Pushed and synced 1 branches

$ gh stack sync
✓ Fetched latest main from origin
✓ Trunk main is already up to date

Pushing 1 branch to origin...
✓ Pushed 1 branches

Syncing PRs ...
✓ PR #30 (close-clinkr-cli-entry-point) — Open

✓ Branches synced
  Stacked on main (69c442c)

$ gh stack merge --squash
✗ this stack has not been submitted to GitHub yet; run `gh stack submit` first

The pull request exists and is open. In this reproduction, GitHub also reported the pull request as mergeable and clean.

Expected behavior

The commands should not give conflicting results.

gh stack submit should state that it published a regular pull request but did not create a remote stack object. Alternatively, it should explain that a remote stack requires at least two pull requests.

gh stack merge should handle a local stack with one pull request. It can merge the pull request directly, or it can show an actionable command such as gh pr merge.

Actual behavior

gh stack submit reports that it pushed and synchronized the one-branch stack. It exits successfully.

gh stack merge reports that the same stack was not submitted. It tells the user to repeat the command that already reported success.

Source context

The behavior is also present on the current github/gh-stack main branch at commit ab00aa4a3f2dddc51aa65849c68b391a1b079311.

In cmd/submit.go, syncStack returns false when the stack has fewer than two pull requests:

// The API requires at least 2 PRs to form a stack.
if len(prNumbers) < 2 {
    return false
}

The caller does not use this result:

if stacksAvailable {
    syncStack(cfg, client, s)
    clearPendingModifyState(cfg, gitDir)
}

The command then prints the success message:

cfg.Successf("Pushed and synced %d branches", len(s.ActiveBranches()))

In cmd/merge.go, the merge command requires a remote stack ID or number:

if s.ID == "" && s.Number == 0 {
    cfg.Errorf("this stack has not been submitted to GitHub yet; run `gh stack submit` first")
    return nil, ErrNotInStack
}

Thus, the submit command knows that it did not create a remote stack object. However, it discards that result and reports success.

Environment

gh stack version 0.1.0
Darwin 25.6.0 arm64

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Deviations: none.