When arc has sent target branch data up after D14736, use it in the UI and "Land Revision"
Summary:
Ref T9952. Ref T3462. After D14736, if we have information about the target/"onto" branch, use it in the UI:
- Show "feature (branched from master)" instead of "feature".
- Default "Land Revision" to hit the correct branch.
Test Plan:
- Branched from test with branch tracking.
- Diffed.
- Saw "feature (branched from test)" in UI.
- Saw "test" fill as default in "Land Revision", despite the repository having a different default branch.
Reviewers: chad
Reviewed By: chad
Differential Revision: https://secure.phabricator.com/D14737