Add if-not-set modifier

[peterjaap]

We want to start using this extension to push configuration to production by running bin/magento config:data:import config/store production in our pipeline.

We want to do this to add initial configuration for 3rd party extensions, much like the <default> tag in config.xml files.

However, we only want to do this when no initial value has been set, so basically we want to set a constraint, or an "if" modifier.

I was thinking about something like this;

path/to/config:
    if-not-set: true
    default:
        0: 1

Or

path/to/config:
    if: not-set
    default:
        0: 1

In the second case, the 'not-set' might in the future also be changed to something to introduce constraint based on either values already imported.

[dermatz]

Hey @peterjaap,

I've tried to implement this in my branch.
Maybe it's what you need? Can you test it?

#81

[therouv]

@peterjaap Great suggestion! Personally, I prefer the second approach, if: not-set, as it offers more flexibility and allows for adding additional constraints in the future.

@dermatz Thanks for your efforts! I'll provide some feedback in the PR.

[peterjaap]

@dermatz pretty cool, looks good to me! But as per @therouv, maybe we should only support if: not-set to avoid confusion :)