[MERGE] Merge types are provided by a registry

[Martin Pool]

On  7 Feb 2007, Aaron Bentley <aaron.bentley at utoronto.ca> wrote:
> John Arbash Meinel wrote:
> > I know we disagree on this, but I honestly do prefer
> > '--merge-type=diff3' to '--diff3'.
> 
> > As someone else mentioned, doing '--merge-type=unknown' would give an
> > unknown format, rather than an unknown argument.
> 
> Well, you get to pick either invocation :-)
> 
> > I do realize that --diff3 is shorter.

A middle way is to give this a short name so you could say perhaps "-T
diff3" or (if optparse can handle this style) -Tdiff3.

(I am kind of remindeded of the wish for an economist with only one
hand...)

I see Aaron's point about the better discoverability of explicit
options, though we could also consider adding some examples of formats.
-- 
Martin