Re: diff attribute ignored by show and log -p

From: Jeff King <peff@peff.net>
Date: Dec 17, 2009, 20:24 UTC
Message-ID: <20091217202459.GC11367@sigill.intra.peff.net>
In-Reply-To: <76718490912170844i7d5f25d1hc32590b877dbf295@mail.gmail.com>

On Thu, Dec 17, 2009 at 11:44:16AM -0500, Jay Soffian wrote:

Show 8 quoted lines

> > The need to give --ext-diff is mentioned in 72909be (Add diff-option
> > --ext-diff, 2007-06-30) but its log message doesn't 'explain' why external
> > diff isn't used by default and you need to pass that extra option.
> 
> "To prevent funky games with external diff engines, git-log and
> friends prevent external diff engines from being called."
> 
> Seemed reason enough to me.

I don't remember discussing it at that time, but much later when touching the external diff code and adding textconv, Junio and I came to the conclusion that textconv was reasonable to do as part of "git log -p", as the result is just an internal conversion that still results in a text diff. Whereas an external diff might be terribly confusing, as it could be spawning graphical viewers or producing output which does not match well with the log output.

> > Probably --ext-diff should be the default?
> 
> Or available via a config option anyway.

If you were going to do such a config option, it might make sense to make it an attribute of the diff driver rather than a global "use external diff". Then each diff driver could say "Yes, I am reasonable to be run as part of log -p".

-Peff