The Branch scope of the local changes view compared only with the
automatic fork point. Its header now names the checked-out branch and a
searchable base branch menu that lists the automatic fork point, then
remote-tracking and local branches; a chosen branch compares with its
merge base with HEAD. The choice lives in the view tab, a missing or
unrelated branch offers the default instead of a retry, and local Branch
review quotes name the base they were compared with.
Refs #7781
