[MERGE] log mainline only by default

[Ian Clatworthy]

Matthew D. Fuller wrote:
> On Thu, Mar 26, 2009 at 03:01:41PM -0500 I heard the voice of
> John Arbash Meinel, and lo! it spake thus:
>> So you could do:
>>     revno: 118 [merge use -n0 to see children]
> 
> I would as soon see it at the end of the log for that rev; where the
> merges would show up if they were shown.
> 
> e.g.,
> ------------------------------------------------------------
> revno: 12345
> [...]
> message:
>   Do stuff blac blah blah
>     [6 merged revs elided: use -n0 to show]

We know whether a revision is a merge or not by looking at the parent count.
We don't know the *number* of merged revisions hidden though cheaply, i.e.
we'd need to calculate the full graph to give the right number.

Both --short and --line simply have [merge] included in the output.
I think --long ought to do the same.

If we want to say 'use -n0 to show merged revisions', we ought to do
it for all formats, not just --long IMO.

Ian C.