FR: allow multiple user config files

[mikejsavage]

Hi,

I develop on several computers and would like to be able to have machine specific jj configs.

I will preface this by saying it's not very important and you can already do it with machine specific shell aliases and --config-toml.

Generally software lets you do this by having a shared main config, which includes a local config (which might not exist) with machine specific stuff in, e.g. for git in WSL I have:

> cat ~/.gitconfig
...
[include]
    path = .gitconfig.local
> cat ~/.gitconfig.local
[core]
        fileMode = false

Less commonly, some software (fish shell) loads everything from a config dir in alphabetical order, so you can do 0-base.fish/1-local.fish to achieve the same thing.

For a concrete example of why this would be helpful for jj, I have [ui] paginate = "never" on Windows because jj launches the pager when everything would fit on one screen and my WSL pager renders escape chars as ESC, making jj quite unusable

[shanesveller]

I make use of Git's includeIf to set things like user.email or commit templates based on whether a project is personal/OSS/professional, and I miss that opportunity as well as basic includes as mentioned here.

[yuja]

We'll add some includeif-like feature, but the implementation isn't started yet.
#616

[martinvonz]

We also have a TODO about maybe reading all config files in ~/.config/jj/ (I think we would simply delete the config_dir.push("config.toml"); line):

jj/cli/src/config.rs

Lines 416 to 422 in a6c18e8

	// TODO: Should we drop the final `/config.toml` and read all files in the
	// directory?
	let platform_config_path = ConfigPath::new(self.config_dir.map(|mut config_dir| {
	config_dir.push("jj");
	config_dir.push("config.toml");
	config_dir
	}));

As a workaround, you can actually already set $JJ_CONFIG to a directory path and we'll read all files from there.