Re: [PATCH v6 3/3] vimdiff: add tool documentation

> What is the reason why a user may want to specify them separately?
> 
>  * I want to use this layout when using plain vim but gvim is so
>    different that I want to use a different one from usability's
>    point of view.
> 
>  * The layout I want to use with plain vim, when fed to gvim or
>    nvim, would totally make them misbehave.  I cannot reuse the same
>    layout even if I wanted to.
> 
>  * Depending on the kind of conflict I deal with, I want to use
>    different layouts, but there is no easy mechanism to choose
>    between multiple values I give to mergetool.vimdiff.layout, so I
>    use one layout for vimdiff and another for gvimdiff, and
>    depending on the layout I want to use, I switch between vimdiff
>    and gvimdiff.
> 
>  * Something else?
> 
> If on the other hand, a user may want to stick to a single layout no
> matter which variant of vim is used, it may make more sense to just
> use a single mergetool.vimdiff.layout across all the different
> variants of vim implementations, and possibly, have their own one
> override the most generic "vimdiff" one.  E.g. gvimdiff would use
> mergetool.gvimdiff.layout if exists, or mergetool.vimdiff.layout
> otherwise.