[MERGE] show merge indicators in log --long

[Ian Clatworthy]

Matt Nordhoff wrote:

> I may be misunderstanding when merge indicators are usually used, this
> is probably too complicated, and it shouldn't block this patch anyway,
> but I just want to throw it out there:
> 
> Why only show the indicators when there's one level? If it's showing two
> levels, but the log actually contains three levels of merges, the user
> will be in the exact same situation as today.

The merge indicators are shown on all levels.

The *advice* about -n is only given if a single level is displayed.
(If the user knows enough to use -n2 say, then they know about the
-n flag and don't need to be told about it).

Ian C.