[JacobStephens2]

Summary

Base branch missing on origin
  local branch exists → show safely quoted push command for that branch + set upstream
  no local branch     → explain create/obtain/select recovery
  stop preflight; leave refs, checkout and configuration untouched

The push command uses explicit source and destination branch refs, so a named Base branch works from another checkout even with a same-named tag. Updates the README's quoted guidance.

Closes #295

Evidence

• Before: cargo test --bin thirdshift launch::tests::a_local_base_branch_missing_on_origin_gets_a_working_push_command -- --exact failed: the error only said push it first.
  After: passes; the test executes the suggested command against a temporary origin and verifies the branch and upstream.
• Before: cargo test --bin thirdshift launch::tests::a_base_branch_absent_locally_and_on_origin_gets_no_push_command -- --exact failed while developing the local-present slice: it suggested pushing a nonexistent branch.
  After: passes, including a same-named local tag and unchanged local/remote refs.
• Named-branch coverage executes the suggested command with an apostrophe, shell metacharacters, HEAD, a shadowing tag, and a different checked-out commit. CLI coverage verifies Run, Architect run and Pickup run preflight.
• Validation: cargo check --all-targets, cargo fmt --check, cargo clippy --all-targets -- -D warnings; full cargo test passed (1809 passed, 0 failed, 2 ignored).

Seams under test

• LaunchDirectory::prepare_base_branch: recovery guidance and the suggested command's real Git effects against a temporary origin.
• CLI preflight for a Run and Passes: failure before work, using the selected Base branch.

Unaddressed findings

• Standards: none; 0 findings.
• Spec: none; 0 findings.
• Security: none; 0 introduced findings. Reviewed the pinned merge-base diff and supporting code for shell injection, Git argument/ref confusion, and unintended branch publication.

Both independent reviewers read every changed file: README.md, src/launch.rs, src/run.rs, tests/architect_run.rs, tests/pickup_run.rs, and tests/preflight.rs. Changed files left unread: none.

Security review outcome

No unaddressed introduced findings.

Merge Danger

Door: two-way

Revert restores the previous diagnostic. No state migration or automatic branch repair.

Blast Radius: preflight

Only missing-origin Base branch recovery guidance changes; existing local-ahead behavior stays covered.

Built with codex · gpt-6.1-sol · high