[MERGE] Add merge indication to the line format

[Ian Clatworthy]

Neil Martinsen-Burrell wrote:
> This is another one of the patches that Ian C. suggested would be
> appropriate for novices.  This adds the text "[merge]" to the line
> format of log, so that revisions which are merges are easily identified
> for further scrutiny (such as with ``bzr log --line -n0 -r ...``)

bb: approve

> It was also suggested that with the advent of the -nN options to log, it
> might also be nice to have a similar indication for the long log
> format.  I did *not* do that here because I couldn't figure out a clean
> way to get the revno's for the parent revisions from the information
> that the log formatter has (which is their revision ids).

branch.revision_id_to_dotted_revno(revision_id) should do the trick?

(If you're keen, make that a separate patch now as this one is useful
as is.)

> As an aside, there are now lots of separate log-related items in NEWS. 
> I don't know if we ever edit NEWS to be more readable and less
> indicative of every single separate contribution, but since 1.12 looks
> like our "Loggy" release, maybe we should consider putting something
> more polished in the release notes.

I expect Martin (as Release Manager) will put some nice summary at the
top and hopefully mention the log improvements. :-) The nature of that
will depend a bit on what gets landed by the close off time, of course.

Ian C.