`tg info` shows bogus "Needs update" with 0 commits

[greenrd]

This only seems to occur with TopGit branches that depend on one or more other TopGit branches:

[user@work topgit]$ tg info t/summary-sort-order
Topic Branch: t/summary-sort-order (11/6 commits)
Subject: Specify the sort order of tg summary.
Base: 3242b63
Remote Mate: origin/t/summary-sort-order
Depends: t/summary-deps-as-function
Needs update from:
        t/summary-deps-as-function (0/0 commit)