sorbet: Add a RBI file for utils/svn.rb typechecking

[issyl0]

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• Needed to include Kernel otherwise Sorbet couldn't find the system_command method.
• I've also attempted to construct method signatures for all the methods.
• Before, brew typecheck surfaced 36 errors. Now we're down to 33 errors.

[reitermarkus]

Needed to include Kernel otherwise Sorbet couldn't find the system_command method.

Is there a way to include this globally? This is included in all Ruby objects inheriting from Object.

[vidusheeamoli]

Needed to include Kernel otherwise Sorbet couldn't find the system_command method.

Is there a way to include this globally? This is included in all Ruby objects inheriting from Object.

From Sorbet's documentation: Kernel is included in Object (which classes default to inheriting from), but not on BasicObject (which classes can optionally inherit from).

Sorbet requires that we explicitly require Kernel in all our modules.

[vidusheeamoli]

Looks good to me! This PR, along with #8707 and #8706 would take down errors from 36 to 18. 🎉

[reitermarkus]

From Sorbet's documentation: Kernel is included in Object

Then why isn't it included in every module? Don't modules inherit from Object? Or does it distinguish between the stdlib's Kernel and our extension to it?

[issyl0]

Is there a way to [include Kernel] globally? This is included in all Ruby objects inheriting from Object.

That would be nice - we're up to 21 separate include Kernel lines in our handwritten RBI files now! The Sorbet docs (step 4) recommend include Kernel explicitly, and another blog post I found states:

To resolve this, I need to include Kernel in the module. I suppose this will be necessary on every class that calls raise. This seems a shame since the Kernel module is already included in every ruby Object class (cite), though I understand one can override methods like puts, raise, and sleep if you really wanted to.

[reitermarkus]

I guess you could theoretically include a module in a BasicObject, that's why it needs to be explicit.