Module worktree_batch 

Primitives shared by the batch-worktree git engines — worktree_rebase and worktree_push.

Both engines answer the same two questions before they do anything specific: which worktrees is this batch about, and what is checked out in each. They also both need one carefully-configured git subprocess seam. Extracting that common half here keeps a second engine from re-deriving it — the two would drift, and the subprocess seam in particular encodes a non-obvious environment-snapshot rule (see [run_git_in]) that is not safe to re-invent.

Nothing here decides anything: classification, the mutation, and the outcome shapes belong to each engine.

Enums

Selection

Which worktrees a batch operation should target.