How to correctly deal with dmd.conf with multiple dmd installations - [ref osx, brew, digger]

[aliak]

Alo,

I'm wondering what’s the deal with dmd.conf and what’s the 
correct way to handle it with dmd installations.

Scenario: `brew install dmd` puts dmd in `/usr/local/bin/dmd` 
(symlink) and sets the `SYSCONFDIR` in its build config so 
`dmd.conf` is in `/usr/local/etc/dmd.conf`.

AFAICT: that seems correct. Is it?

The problem comes with tools like digger. Which seems to be part 
of DMD’s PR process as D bot seems to love it :) so I guess it's 
officially supported? - plus it seems super convenient for dmd 
development.

But anyway, it’s broken on the mac if you use brew (and brew is 
[probably?] defacto). There is a workaround when running `digger 
build` but it’s not nice, and you’d never be able to guess it, 
and it’s error prone [0].

When you do `digger install` it seems to not “install” a 
`dmd.conf` but it does install the `dmd` binary in 
`/usr/local/bin/dmd` - but that wasn’t built with `SYSCONFDIR` so 
it doesn’t find `/usr/local/etc/dmd.conf` either, but even if it 
did, that’s the wrong `dmd.conf` (i.e. not the one that the build 
was based on - so would it even point to the right env?).

So basically, is dmd.conf supposed to go along with an ad hoc 
installation of dmd?

And, is dmd.conf necessary or can I safely ignore its existence? 
(it seems like maybe dub depends on it though so maybe not).

Cheers,
- Ali

[0]: https://github.com/CyberShadow/Digger/issues/74