Add controls to select base and tip commits in the RB.DiffCommitListView

Review Request #10132 — Created Aug. 30, 2018 and submitted — Latest diff uploaded

Information

Review Board
release-4.0.x
3391784...

Reviewers

The RB.DiffCommitListView can now optionally display controls for
selecting between base and tip commits to control what will be displayed
in the diffviewer. The actual logic for changing the diffs is not yet
implemented -- just the control itself.

Ran JS tests.