Set GL_REPOSITORY in update hooks for API-initiated requests

GL_REPOSITORY is not set in update hooks for API-initiated requests, and probably not set for other web-initiated requests. It is set consistently for pre-receive hooks; and set in update for git pushes. This is needed so update hooks can always know which repository they are working with.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information