Path-level export filtering. Tracker audience is the default filter and
flags are the override; there is no hunk privacy, no AST rewriting, and
no concealment claim. The filter decides which files are copied out of
a workspace — nothing more.
Decide what leaves the workspace. Nothing is copied here — a plan is
worth having on its own, because --dry-run and the failure message both
need it before any file moves.
A destination must be absent or empty — export writes a fresh repository,
and quietly merging into someone’s existing directory is the kind of
surprise that loses work.