Summary:
Ref T7100. When a user navigates to a branch like "default" which is ambiguous:
- don't fatal;
- choose one alternative to resolve it to (currently more or less at random);
- sometimes show what we did in the UI.
Also, add a new table to show the alternatives.
This will get refined in followup changes.
Test Plan:
{F384335}
{F384336}
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T7100
Differential Revision: https://secure.phabricator.com/D12547
