fix: bundle transport fails when agent commits to HEAD instead of named branch

[Copilot]

When the Copilot agent commits changes to the current checkout branch (HEAD) rather than first creating the target branch locally, the git bundle is created with ${GITHUB_SHA}..HEAD — bundling the checkout branch ref (e.g. refs/heads/copilot/make-bundle-default-patch-format) instead of the agent-requested ref (refs/heads/jsweep/clean-remove-trigger-label). create_pull_request.cjs then fails with fatal: couldn't find remote ref refs/heads/jsweep/clean-remove-trigger-label.

Changes

• generate_git_bundle.cjs: In Strategy 2, before bundling ${GITHUB_SHA}..HEAD, create a local branch pointing to HEAD (git branch -f <branchName> HEAD) so the bundle always advertises refs/heads/<branchName>:

  - execGitSync(["bundle", "create", bundlePath, `${githubSha}..HEAD`], { cwd });
  + execGitSync(["branch", "-f", branchName, "HEAD"], { cwd });   // create the named ref
  + execGitSync(["bundle", "create", bundlePath, `${githubSha}..${branchName}`], { cwd });

[pelikhan]

@copilot

remove fallback:

create_pull_request.cjs — defensive fallback: If the expected refs/heads/ ref is still absent from the bundle (any future edge case), run git bundle list-heads and use the first available refs/heads/* ref rather than failing immediately.

[Copilot]

@copilot

remove fallback:...

Done — removed the fallback in c6ba266.

[Copilot]

Pull request overview

Fixes git bundle generation when the agent commits on the currently checked-out branch (HEAD) instead of first creating the requested local branch, ensuring the resulting bundle advertises the expected refs/heads/<branchName> ref so create_pull_request.cjs can fetch it reliably.

Changes:

• In generate_git_bundle.cjs Strategy 2, create/force-update a local branch ref pointing at HEAD before bundling.
• Bundle the commit range as ${GITHUB_SHA}..${branchName} (falling back to ${GITHUB_SHA}..HEAD if branch creation fails).

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[Copilot]

branchName is user-/agent-controlled and may begin with "-". In git branch -f <branchName> HEAD, a leading dash can be parsed as another option (git requires -- to allow such branch names), which is both a correctness and hardening issue. Elsewhere you already defend against this (e.g., generate_git_patch.cjs uses -- when passing branch names to git fetch). Consider adding -- before branchName here (or using update-ref with an explicit refs/heads/... refname) so branch names can’t be interpreted as flags.

Suggested change

	execGitSync(["branch", "-f", branchName, "HEAD"], { cwd });
	// Use -- so a branch name beginning with "-" is not parsed as another option.
	execGitSync(["branch", "-f", "--", branchName, "HEAD"], { cwd });

[pelikhan]

@copilot

Review comments

[Copilot]

@copilot

Review comments

Applied the review suggestion in 5cf8908 — added -- before branchName in git branch -f so branch names starting with - can't be misinterpreted as flags.