You could probably learn a lot from git-mergetool:

manpage: http://www.kernel.org/pub/software/scm/git/docs/git-mergetool.html

code: http://github.com/git/git/blob/master/git-mergetool.sh

On Fri, Feb 27, 2009 at 12:48:03PM +0000, Samuel Bronson wrote:
> You could probably learn a lot from git-mergetool:
> manpage: http://www.kernel.org/pub/software/scm/git/docs/git-mergetool.html
> code: http://github.com/git/git/blob/master/git-mergetool.sh

IMO that would be a third-party wrapper, separate from the Darcs
binary itself.  If you like, you can provide a patch adding such a
wrapper to the tools/ subdir.  There are already examples in the user
manual giving example invocations for some tools.

On Sat, Mar 28, 2009 at 7:10 AM, Trent Buck <bugs@darcs.net> wrote:
> IMO that would be a third-party wrapper, separate from the Darcs
> binary itself.  If you like, you can provide a patch adding such a
> wrapper to the tools/ subdir.  There are already examples in the user
> manual giving example invocations for some tools.

Well, okay, but you can still only store one of those commands in the
configuration file at a time, and I'm not going to buy that people are
actually expected to type those long messy flags in during normal
usage ...

On Sun, Mar 29, 2009 at 02:22:44AM -0000, Samuel Bronson wrote:
> 
> Samuel Bronson <naesten@gmail.com> added the comment:
> 
> On Sat, Mar 28, 2009 at 7:10 AM, Trent Buck <bugs@darcs.net> wrote:
> > IMO that would be a third-party wrapper, separate from the Darcs
> > binary itself.  If you like, you can provide a patch adding such a
> > wrapper to the tools/ subdir.  There are already examples in the user
> > manual giving example invocations for some tools.
> 
> Well, okay, but you can still only store one of those commands in the
> configuration file at a time, and I'm not going to buy that people are
> actually expected to type those long messy flags in during normal
> usage ...

Are you saying that you want to be able to regularly use more than one
merge tool, and switch between them using some kind of dedicated
command-line option?  I don't understand why -- surely you find a
merge tool you like, and then you stick with it?

On Sat, Mar 28, 2009 at 11:08 PM, Trent Buck <bugs@darcs.net> wrote:

> Are you saying that you want to be able to regularly use more than one
> merge tool, and switch between them using some kind of dedicated
> command-line option?  I don't understand why -- surely you find a
> merge tool you like, and then you stick with it?

What if my preferred tool uses X, but sometimes I'm SSHing in with, oh, PuTTY?

On Sun, Mar 29, 2009 at 03:15:59AM -0000, Samuel Bronson wrote:
> On Sat, Mar 28, 2009 at 11:08 PM, Trent Buck <bugs@darcs.net> wrote:
> 
>> Are you saying that you want to be able to regularly use more than one
>> merge tool, and switch between them using some kind of dedicated
>> command-line option?  I don't understand why -- surely you find a
>> merge tool you like, and then you stick with it?
> 
> What if my preferred tool uses X, but sometimes I'm SSHing in with, oh, PuTTY?

The wrapper would obviously be smart enough to detect that.  I have
such wrappers for $BROWSER and $EDITOR, and I see no reason it could
not apply equally well to a wrapper to select the appropriate merge
tool.

http://twb.ath.cx/Preferences/.bin/twb-browser
http://twb.ath.cx/Preferences/.bin/twb-editor
http://twb.ath.cx/Preferences/.bin/twb-emacsclient

While I agree that having to pass in complex command line arguments to
--external-merge is a problem, I think we should avoid making darcs more complex
to deal with this case.

For what it's worth, on my Mac, I have
  alias darcs-gdiff='darcs diff --diff-command '\''opendiff %1 %2'\'
and on Linux
  alias darcs-gdiff='darcs diff --diff-command='\''meld %1 %2'\'''

Note also that I would not particularly mind seeing a single distinguished merge
tool and diff command to which darcs will automatically pass in the right arguments.

In other words that if you do "darcs apply --external-merge='git-mergetool
--tool=opendiff --foo'", it is equivalent to "darcs apply
--external-merge="'git-mergetool --tool=opendiff --foo %1 %2 %a %b'"

Basically, if you can find a way to keep darcs simple while achieving the
objective of making external merge easier to use, then great!