Scroll the selection into view after a filtering mode change

The commit list a filtering mode change leaves behind has nothing to do
with the one that was showing, so the scroll position it inherits says
nothing about where the selection ended up, and the selection can land
anywhere off screen. PostRefreshUpdate only moves the cursor within the
existing scroll position, so ask for the scroll separately, the way the
commits refresh does when it moves the selection itself.

Exiting filtering mode looked like it worked, but only by accident: the
commits refresh recognizes the commit that was selected before it ran,
selects it again at its new index, and scrolls because the index moved.
That does nothing for the case where the commit is gone from the list, or
for entering filtering mode, where we select the first commit ourselves.

pkg/gui/controllers/helpers/mode_helper.go

@@ -270,6 +270,11 @@ func (self *ModeHelper) changeFiltering(setFilter func(), selectCommit func()) e
 
 				selectCommit()
 				self.c.PostRefreshUpdate(self.c.Contexts().LocalCommits)
+				// The list we just selected in has nothing to do with the one
+				// that was showing, so wherever it was scrolled to says nothing
+				// about where the selection now is. PostRefreshUpdate leaves the
+				// scroll position alone, so ask for it separately.
+				self.c.Contexts().LocalCommits.FocusLine(true)
 				return nil
 			},
 		})