Sameen Karim 756002b4c9 ensure local trunk branch for required operations (#127) ...

* Ensure trunk branch exists locally before commands that need it

When a user starts a stack after renaming their initial branch
(e.g. `git branch -m newbranch`), the trunk branch (e.g. main) may
not exist as a local branch. Commands that pass the trunk name to git
operations like merge-base, rebase, or rev-parse then fail with:

  fatal: Not a valid object name main

Add an `ensureLocalTrunk` helper that checks whether the trunk branch
exists locally and, if not, fetches it from the remote and creates a
local tracking branch. This mirrors the pattern already used in the
checkout command for importing stacks.

Commands updated:
- modify: call ensureLocalTrunk before the linearity check in
  CheckStackLinearity, which uses IsAncestor(trunk, branch). This was
  the originally reported failure.
- rebase: call ensureLocalTrunk after fetch and before fastForwardTrunk
  and the cascade rebase. git rebase requires a locally resolvable ref;
  the remote tracking ref alone is not sufficient.
- trunk: call ensureLocalTrunk before CheckoutBranch so that
  `gh stack trunk` works even when trunk was never created locally.
- checkout: refactor the existing inline BranchExists + CreateBranch
  block to use the shared helper.

Also fix an incorrect comment in fastForwardTrunk that claimed "the
remote tracking ref is sufficient for rebasing" — verified empirically
that `git rebase main` fails when main has no local branch, even after
fetching origin/main.

Commands that were already safe and required no changes:
- sync: fetches trunk explicitly and fastForwardTrunk guards with
  BranchExists
- push, switch, navigate, unstack: do not reference trunk
- add, submit: do not require trunk as a local git ref
- view: handles IsAncestor errors gracefully (false positive is
  acceptable since rebase will fix it)

* add check to avoid unnecessary remote selection prompt

2026-06-15 13:54:20 -04:00

1.5 KiB

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