submit --auto fills every new PR with the raw template, with no way to supply a body

[mark-bookedworks]

What happens

gh stack submit --auto copies .github/pull_request_template.md into every new PR verbatim, and there is no flag to supply a body instead. Every PR in the stack lands with the template's <!-- ... --> placeholders intact and its checklist unchecked.

Repro on a repo that has a PR template:

gh stack init layer-a layer-b layer-c
# commit on each layer, each with a meaningful commit body
gh stack submit --auto --open
gh pr view <any-layer> --json body --jq .body
# -> the raw template, placeholders and all; the commit body is gone

We hit this on a 3-layer stack. All three PRs opened with unchecked - [ ] All tests passing locally boxes sitting directly above fully green CI, which reads to a reviewer as though nothing had been verified. The rationale we had written into each commit body was discarded.

Why --auto isn't optional for us

The interactive TUI added in #147 solves this nicely for humans: you edit each description before submitting. But --auto skips the editor, and it is mandatory for any non-interactive caller. GitHub's own agent skill for this extension states the rule plainly:

Always use --auto with gh stack submit to auto-generate PR titles. Without --auto, submit prompts for a title for each new PR.

So agents and CI must pass --auto, and --auto is exactly the path with no way to provide a body. The result is that agent-created stacked PRs land with unfilled scaffolding by default rather than by oversight.

There is also a smaller inconsistency inside --auto itself. Titles fall back intelligently (commit subject for a single commit, humanized branch name otherwise), but bodies do not fall back at all: the template wins even when a perfectly good commit body exists.

Not a duplicate, but related

• pull requests created with `gh stack submit` do not use the pull request readme template #53 asked for template support in submit. That was delivered in use PR template when opening PRs #77 and expanded in Add an interactive submit TUI for customizing each PR's title, description, and draft state #147. This report is about the interaction between that feature and --auto, which pull requests created with `gh stack submit` do not use the pull request readme template #53 predates.
• For single commits, load that commit message as the PR description #359 asks for commit-message-as-description, but specifically for gh stack link from a Sapling workflow. Overlapping motivation, different command and different cause.

What would fix it

In rough order of preference:

1. A body flag on submit, per branch. Something like --body-file <branch>=<path> (repeatable), or simply honouring --body-file for a single-layer submit. This is the general fix and covers agents, CI, and scripted use.
2. Make --auto fall back to the commit body the way it already falls back for titles: single commit on the branch means commit subject as title and commit body as description, with the template used only when the commit has no body. This matches what git push-created PRs do and would have fully solved our case.
3. Failing both, do not apply the template under --auto. An empty body is more honest than a template that looks filled in but is not, and it is far easier to detect afterwards.

Happy to test a prerelease against a real stack if that is useful.

Environment

• gh 2.93.0, gh-stack v0.1.0, Linux
• Repo has .github/pull_request_template.md with 6 comment placeholders