GitLab

* Save FSDP metadata for offline unflattening

* Complete the meta-data saving method with all the information needed to reconstruct a checkpoint offline, and implement the method that reconstruct a consolidated checkpoint from a sharded checkpoint

* Complete the meta-data saving method with all the information needed to reconstruct a checkpoint offline, and implement the method that reconstruct a consolidated checkpoint from a sharded checkpoint

* Add a unit test to show how to use the function

* Code review + improvement of the unit tests

* Code review: extract clean_path

* Make meta data and consolidation of checkpoint work for flatten_parameter=False

* Add new unit test file in CI

* Complete changelog and fix mypy issues

* Add support for module buffers in the consolidation of sharded checkpoints

* Better support for module buffers: save them in the meta data

* Refactoring: use a data-format for the meta data that is simpler to understand (move from object of array to array of object format)

* Renaming to make code clearer

* Code review: in_temporary_directory rework and typo correction

* Renaming
Co-authored-by: Sam Shleifer <sshleifer@gmail.com>
Co-authored-by: QuentinDuval <QuentinDuval@users.noreply.github.com>