Hi Jeff, On Mon, Apr 22, 2019 at 02:18:36PM -0400, Jeff Hostetler wrote: > > > On 4/22/2019 1:07 AM, Denton Liu wrote: > >In git-difftool.txt, it says > > > > 'git difftool' falls back to 'git mergetool' config variables when the > > difftool equivalents have not been defined. > > > >However, when `diff.guitool` is missing, it doesn't fallback to > >anything. Make git-difftool fallback to `merge.guitool` when `diff.guitool` is > >missing. > > > > Is this a well-defined operation? I believe this is a yes. > > I mean, we're assuming here that a 3-way gui merge tool (that probably > expects 3 input pathnames and maybe a 4th merge-result pathname (and > associated titles and etc)) can function sanely when only given the > pair that a diff would have. > > That is, we're assuming that the selected merge tool has a 2-way diff > mode and that the command line args for the 2- and 3-way views are > compatible. If I read the code correctly, it seems like the only tool that is strictly "merge-only" is tortoisemerge. In mergetools/tortoisemerge, we have can_diff () { return 1 } which means it will refuse to run as a difftool. In the case where it fails like this, it'll loudly complain to the user, which'll give them a chance to fix their config. I believe that this is desired behaviour and the patch adds on top of that. Thanks, Denton > > Just a thought > Jeff > >