Re: [PATCH 3/4] diff: introduce diff.<driver>.binary

> The "diff" gitattribute is somewhat overloaded right now. It
> can say one of three things:
> 
>   1. this file is definitely binary, or definitely not
>      (i.e., diff or !diff)
>   2. this file should use an external diff engine (i.e.,
>      diff=foo, diff.foo.command = custom-script)
>   3. this file should use particular funcname patterns
>      (i.e., diff=foo, diff.foo.(x?)funcname = some-regex)
> 
> Most of the time, there is no conflict between these uses,
> since using one implies that the other is irrelevant (e.g.,
> an external diff engine will decide for itself whether the
> file is binary).
> 
> However, there is at least one conflicting situation: there
> is no way to say "use the regular rules to determine whether
> this file is binary, but if we do diff it textually, use
> this funcname pattern." That is, currently setting diff=foo
> indicates that the file is definitely text.

> This patch introduces a "binary" config option for a diff
> driver, so that one can explicitly set diff.foo.binary. We
> default this value to "don't know". That is, setting a diff
> attribute to "foo" and using "diff.foo.funcname" will have
> no effect on the binaryness of a file. To get the current
> behavior, one can set diff.foo.binary to true.