R1:2bfc5ff92ec2

Modernize more Diffusion controllers

Summary: Ref T4245. Standardize how context is read, minor updates / modernizations / consistency tweaks.

Test Plan:
- Viewed a change.
- Viewed brnaches.
- Edited a commit.
- Viewed tags.
- Viewed history.
- Added, edited and deleted a mirror.
- Viewed push events.
- Viewed a particular event.
- Viewed ref disambiguation.
- Viewed repository list.
- Ran automation test.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4245

Differential…