Purpose
-------
FS-539: the ``oct migrate`` subpackage, which moves a project onto the
Option C ``.option_c/`` layout. This file is the package shell only; the
command and every migration step live in
:mod:`oct.migrate.oct_migrate`.
Responsibilities
----------------
- Expose ``migrate_group`` as this package's single public name.
- Resolve it LAZILY through :func:`__getattr__`, so importing
``oct.migrate`` alone does not import click or the migration engine.
``oct.cli`` does resolve it at import, to register the command.
Diagnostics
-----------
Domain: OCT-MIGRATE
Levels:
L1 - errors: none raised here; the engine owns failure reporting
L2 - (none) the lazy re-export resolves before diagnostics start
L3 - (none) the migrate command reports in its own module
L4 - (none)
Contracts
---------
- Import-time side effects: none beyond the ``_dbg`` shim. No migration
submodule is imported until an attribute is requested.
- Emits no ``_dbg`` record: ``__getattr__`` runs during ``import oct.cli``,
before ``oc_diagnostics.init()``, so a record here printed the "called
before init()" RuntimeWarning on every oct invocation (plan 263's rule
for lazy package roots; found again by the chart C runtime trace,
2026-09-27).
- Any name other than ``migrate_group`` raises ``AttributeError``, so a
typo fails loudly instead of returning ``None``.
- ``__all__`` and :func:`__getattr__` must agree; a name added to one
without the other is unreachable or undeclared.
Dependencies
------------
- oct.migrate.oct_migrate (lazy; the migrate command, resolved inside __getattr__)
- oct.core.diagnostics (_dbg structured logger, imported but not called)
1.15.0