Improve base branch resolution for cross-repo PRs

[dsyme]

For cross-repo PRs, getBaseBranch() needed to become dependent on the target repo

This does structural work to get that to happen

[Copilot]

Pull request overview

Updates base-branch resolution so cross-repo PR operations resolve the base branch against the configured target repository (not the workflow repo), and threads that base branch into patch generation.

Changes:

• Add an optional targetRepo parameter to getBaseBranch() so issue_comment PR base lookups can query the correct repository.
• Make generateGitPatch() take an explicit baseBranch argument and update callers/tests accordingly.
• Resolve the configured target repo (via repo_helpers) in safe-output handlers and other entrypoints before calling getBaseBranch().

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
actions/setup/js/safe_outputs_handlers.test.cjs	Adds a mocked global.context needed by target-repo resolution in handler tests.
actions/setup/js/safe_outputs_handlers.cjs	Resolves target repo before calling getBaseBranch() and passes resolved base branch into generateGitPatch().
actions/setup/js/push_to_pull_request_branch.cjs	Parses configured target repo and passes it into getBaseBranch() for cross-repo correctness.
actions/setup/js/git_patch_integration.test.cjs	Updates integration tests to pass an explicit base branch into generateGitPatch().
actions/setup/js/get_base_branch.test.cjs	Adds coverage for the new optional targetRepo parameter.
actions/setup/js/get_base_branch.cjs	Implements targetRepo support for issue_comment PR base-branch API lookup.
actions/setup/js/generate_git_patch.test.cjs	Updates tests for the new generateGitPatch(branch, baseBranch, options) signature.
actions/setup/js/generate_git_patch.cjs	Changes patch generation to rely on a caller-provided base branch (no internal getBaseBranch() lookup).
actions/setup/js/create_pull_request.cjs	Parses configured target repo and passes it into getBaseBranch() for cross-repo correctness.
actions/setup/js/create_agent_session.cjs	Parses configured target repo and passes it into getBaseBranch() for cross-repo correctness.

Comments suppressed due to low confidence (1)

actions/setup/js/safe_outputs_handlers.cjs:199

• resolveTargetRepoConfig() ultimately falls back to context.repo (repo_helpers.getDefaultTargetRepo). In the MCP server entrypoint (safe-outputs-mcp-server.cjs), only global.core is shimmed (shim.cjs) and global.context is not set, so invoking create_pull_request via the MCP server can throw a ReferenceError when no target-repo/GH_AW_TARGET_REPO_SLUG is configured. Consider adding a local fallback here (e.g., prefer prConfig["target-repo"], then process.env.GH_AW_TARGET_REPO_SLUG, then process.env.GITHUB_REPOSITORY) and/or explicitly error with ERR_CONFIG when none are available instead of relying on context.

    // Resolve target repo for base branch resolution (cross-repo scenarios)
    const prConfig = config.create_pull_request || {};
    const { defaultTargetRepo } = resolveTargetRepoConfig(prConfig);
    const targetRepoParts = parseRepoSlug(defaultTargetRepo);
    const baseBranch = await getBaseBranch(targetRepoParts);

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

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