Codegen: Do less work in dry-runs for sharded files (#69805)
Summary:
This improves a dry-run of `gen.py` from 0.80s to 0.45s.
`FileManager` in `dry_run` mode doesn't actually need to compute the
environment; it just records the filenames that would have been
written.
cc ezyang bhosmer bdhirsh
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69805
Reviewed By: ngimel
Differential Revision: D33944912
Pulled By: albanD
fbshipit-source-id: 74f22af3f2bd5afdef7105961270198566fa91e5
(cherry picked from commit 6fcdc15954788257b76e14087ba1ebf63fd3ab27)
