wt-switch-create

Arguments: `$ARGUMENTS`. Grammar: `[<branch>] [<repo>] [-- <task>]`.

- **branch** — optional; the branch name for the new worktree. When omitted,
  pick one (step 1 below).
- **repo** — optional path; create the worktree in this repo instead of the
  session's current one.
- **task** — optional; what to do inside the new worktree. No task means enter
  the worktree and wait.

Tokens before the `--` are the branch and/or repo: a path-shaped token
(starting with `/`, `~`, `./`, or `../`) is the repo; any other token is the
branch (`docs` is a branch name, never the `docs/` directory). More than one
branch-shaped token before a `--` doesn't fit the grammar — ask. Without a
`--`, judge where the task starts: leading tokens that read as a branch name
(`fix-auth`) or a repo path are consumed as such, and the rest is the task;
otherwise the whole input is the task (`fix the parser bug` has no
branch-shaped lead — all task).

```
/wt-switch-create my-feature -- fix the parser bug
/wt-switch-create -- fix the parser bug
/wt-switch-create my-feature ~/workspace/other-repo -- fix the parser bug
/wt-switch-create my-feature
```

## What to do

Steps 1–3 come before any other work.

<!-- Maintainers: rationale.md (same directory) covers the harness rules and
design choices behind this — read it before re-adding guards or routes. -->

1. **Pick the branch name** if none was given: short, from the task and
   consistent with existing worktree names, or, mid-session, from the work
   being moved; with nothing to derive from, ask.

2. **Create the worktree** with a `Bash` call (omit `-C <repo>` for this repo):

   ```
   wt -C <repo> switch --create <branch> --no-cd --format=json
   ```

   Stdout is JSON whose `path` field is the worktree's absolute path (status
   lines go to stderr). On `Branch <branch> already exists`: if the user named
   the branch, rerun without `--create` (it enters the branch, creating its
   worktree if missing); if step 1 picked the name, pick another and rerun. Any
   other failure (not a git repo, invalid name): report it and stop.

   Mid-session, carry uncommitted work across: `git stash push -u` before
   creating the worktree, then `git -C <path> stash pop` after (the stash is
   shared across worktrees).

3. **Enter the worktree, then do the task.** Call
   `EnterWorktree({path: "<path from the JSON>"})`.

   - **Accepted** → the session is re-rooted in the worktree. Do the task (or,
     with no task text, confirm it's ready and wait).
   - **Rejected** → graceful, and nothing is created. `EnterWorktree`
     re-roots only into a worktree the session is permitted to enter, and that
     permitted set is fixed by two factors: the repo your cwd resolves to, and
     the session's state. Each rejection is just that set coming up empty or
     without the target: no repo resolves (cwd is outside any git repo, e.g. a
     non-git parent such as `~/workspace` that only holds repos, as in a
     background job), which fails with `the current directory is not in a git
     repository`; the target belongs to a different repo than the one resolved;
     or the session is already rooted in a worktree (or is a pinned agent), a
     state that narrows the set to the resolved repo's `.claude/worktrees/` and
     so excludes even a same-repo `wt` sibling. All reduce to the same recovery
     test: whether you can `cd` into the worktree, which works when it's inside
     an allowed directory (a `permissions.additionalDirectories` entry such as
     `~/workspace`). So `cd <path>` and read the result:
     - no `Shell cwd was reset` notice → it stuck; the worktree is reachable.
       Work there, but a bare `cd` is not a tracked re-root, so the cwd can
       revert to the session's launch worktree across turns (and in spawned
       subagents); pin commands with `git -C <path>` / `wt -C <path>` rather
       than trusting the `cd` to persist.
     - `Shell cwd was reset` → not reachable. Stop and ask the user to make it
       reachable: add the repo, or a parent like `~/workspace`, to
       `permissions.additionalDirectories` (durable, every session), or run
       `/add-dir <path>` (this session). Then continue. Don't grind through
       absolute paths with `cd` resetting on every command.

## Cleanup

The worktree is a normal worktrunk worktree: it persists after the session
ends, shows up in `wt list`, and is merged or removed with `wt merge` /
`wt remove <branch>` like any other. Don't remove it unprompted. If the user
asks to leave mid-session, `ExitWorktree({action: "keep"})` returns the
session to its original directory; `ExitWorktree` cannot remove a worktree
entered by `path`, so removal is always `wt remove <branch>`.

## Scope

This command authorizes creating/entering ONE worktree (in the named repo, if
one was given) and doing the requested task. Commits, pushes, and merges still
each require explicit user permission.