fix(stage): validate public remote URL parsing and surface gh pr create stderr

[andyma-star]

Two gaps in error handling for venfork stage: unparseable public remote URLs silently produced malformed commands, and gh pr create failures swallowed the underlying error reason.

Changes

• Remote URL validation — after parsing the public remote, fail fast with a clear message if publicRepoPath is empty (always) or publicOwner is empty (when --create-pr is set), before any URL/command construction
• gh pr create failure diagnostics — when gh pr create exits non-zero, emit stderr via p.log.warn so users see the actual failure reason (duplicate PR, missing permissions, invalid head/base, etc.)

[Copilot]

Pull request overview

Adds opt-in enhancements to venfork stage to optionally create a draft upstream PR and (optionally) copy title/body from the corresponding open private PR on origin, reducing manual copy/paste when staging work.

Changes:

• Introduces stage-specific CLI arg parsing for --create-pr and --copy-pr-body (with validation).
• Updates CLI routing to parse stage flags and pass options into stageCommand.
• Extends stageCommand to optionally run gh pr create --draft, and optionally prefill title/body from a private PR; adds docs and tests.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/stage-args.ts	Adds parsing/validation for new stage flags.
src/index.ts	Routes stage through the new parser and passes options to stageCommand.
src/commands.ts	Implements optional draft PR creation and private PR title/body copy in stageCommand.
tests/stage-args.test.ts	Adds unit tests for stage arg parsing and validation behavior.
tests/commands.test.ts	Adds tests covering draft PR creation and copy-PR-body flow.
README.md	Documents new stage flags and updated behavior.

Comments suppressed due to low confidence (1)

src/commands.ts:794

• git remote get-url upstream is executed with reject:false but the exit code is not checked. If the upstream remote is missing or the command fails, upstreamRepoPath becomes empty and both the compare URL and gh pr create --repo will be invalid. Consider mirroring the public remote handling here (check exitCode and throw RemoteNotFoundError('upstream'), and/or validate parseRepoPath(upstreamUrl) before continuing).

    const upstreamUrlResult = await $({
      reject: false,
    })`git remote get-url upstream`;
    const upstreamUrl = upstreamUrlResult.stdout.trim();
    const upstreamRepoPath = parseRepoPath(upstreamUrl);

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[Copilot]

publicRepoPath/publicOwner are used to build the compare URL and to set gh pr create --head, but neither value is validated. If the public remote URL isn’t a parseable github.com URL, parseRepoPath/parseOwner will return an empty string and --head ${publicOwner}:${branch} will be malformed. Add validation (e.g., if !publicRepoPath or (when --create-pr) !publicOwner, fail with a clear error) before constructing URLs/commands.

Suggested change

	if (!publicRepoPath) {
	p.log.error(
	"Could not determine the GitHub repository path from the 'public' remote URL. " +
	"Please ensure the 'public' remote points to a valid github.com repository.",
	);
	process.exit(1);
	}
	if (createPr && !publicOwner) {
	p.log.error(
	"Could not determine the GitHub owner from the 'public' remote URL required for --create-pr. " +
	"Please ensure the 'public' remote points to a valid github.com repository.",
	);
	process.exit(1);
	}

[Copilot]

When gh pr create fails, the code only stops the spinner with "Draft PR not created" and discards the actual stderr/exit reason. This makes it hard to diagnose common cases (already-open PR, missing permissions, invalid head/base). Consider logging createResult.stderr as a warning (or including it in the error path) so users know what to do next.

Suggested change

	s.stop('Draft PR not created');
	s.stop('Draft PR not created');
	const stderr = createResult.stderr?.toString().trim();
	if (stderr) {
	p.log.warn(`gh pr create failed: ${stderr}`);
	}

[cabljac]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied both review changes in commit bf9b528:

1. Added validation for publicRepoPath (unconditional) and publicOwner (when --create-pr is set) with clear error messages before constructing any URLs or commands.
2. Logs createResult.stderr as a warning when gh pr create fails so users can diagnose the issue.