Only require view permissions for read-only Git LFS requests
Summary: Ref T7789. Implement proper detection for read-only requests. Previously, we assumed every request was read/write and required lots of permissions, but we don't need "Can Push" permission if you're only cloning/fetching/pulling.
- Set push policy to "no one".
- Fetched, got clean data out of LFS.
- Tried to push, got useful error.
Reviewed By: chad
Maniphest Tasks: T7789
Differential Revision: https://secure.phabricator.com/D15499