System-wide configuration file

[jantari]

Checklist

• I've looked through the documentation and existing open issues for this feature/feature request.

Describe the feature request

First off, thanks a lot for this program. I've used it for a while and it's only been getting better!

One additional feature I'd love for multi-user systems (aka servers or VDI) is the ability to have a system-wide (machine-wide) default configuration file. This is a typical feature of many programs that allows an administrator to pre-configure customized default options for the program in one central configuration file that applies to everyone who logs into the machine, but users are still able to create their own per-user configuration files (same as now) that will override the system-wide defaults.

On Windows, such a system-wide configuration would belong in the "ProgramData" (CommonApplicationData) directory whose location is obtained by calling SHGetKnownFolderPath with FOLDERID_ProgramData as the first argument. Alternatively in managed code it could be a call to GetFolderPath with CommonApplicationData argument but I don't think that's as accessible to Rust.

On Unix-like systems I believe XDG_CONFIG_DIRS should cover this usecase.

[ClementTsang]

Hmm. That's an interesting idea, though my immediate gut reaction is that I'm not sure how much I will prioritize it since this use case seems kinda out of scope.

Maybe I might explore it alongside related ideas like #901?