Derive Macro SettingsGroup 

#[derive(SettingsGroup)]
{
    // Attributes available to this derive:
    #[settings_group]
}

Cheat sheet for derive syntax,

Group Override

#[derive(SettingsGroup)]
#[settings_group(group = "my_group")]
struct MySettings {
    test: true
}

results in:

[my_group]
test = true

File Override

#[derive(SettingsGroup)]
#[settings_group(file = "my_file")]
struct MySettings {
    test: true
}

results in a different file being used as the source of the settings.

Key Override

Only valid for enums, as struct keys are always derived from the field name.

#[derive(SettingsGroup)]
#[settings_group(key = "my_key")]
enum MySettingsEnum {
    Variant1,
    Variant2
};

results in:

[my_settings_enum]
my_key = "variant1"