Allow CLI configuration to be saved to a file

[amisevsk]

Describe the problem you're trying to solve
As the CLI becomes more complex and gains more options, it would be convenient to be able to set some/all of them persistently in a configuration file. This will become increasingly useful as e.g. more networking options are added.

Describe the solution you'd like
Kit should provide a kit config command to allow configuring common options available as flags and saving that configuration between invocations. This configuration should be saved to some file (maybe in the $KITOPS_HOME directory, or separate Kit config directory) and these settings should be used instead of default values for corresponding flags.

Describe alternatives you've considered
Mainly, deferring this work until there are enough flags we're specifying on every invocation where the moderately increased complexity of supporting a config file makes sense.

Additional context
Related: #365 -- we want to be able to persistently disable update notifications, for example.

[SkySingh04]

This sounds like a fun and interesting issue to work on! This will require a little bit of work but lets do this!

I had a question : are we supposed to store config for all flags for all commands or for just the root command?

[bartoszmajsak]

This is my first activity here, so 👋🏻 :)

@amisevsk @gorkem One thing I wonder - was viper integration with Cobra considered? That allows to define config sources (and their precedence) like env vars, and files (multiple formats) seamlessly.

[gorkem]

@bartoszmajsak we used viper on the early days for a small case. @amisevsk found a way to do it without it and we removed. Perhaps, we do have more of a use for it now to reconsider.

[amisevsk]

Yeah, we considered viper but I found (at least early on) that it was not a great fit. It may make sense to use now, though we've still only got ~2-3 config settings (log level, progress bars), that make sense to set persistently. I agree it might be worth revisiting (though I remember thinking actually using viper in commands was somewhat cumbersome)

[bupd]

I remember thinking actually using viper in commands was somewhat cumbersome

@amisevsk
A better approach might be to move the viper setup into a separate package and have it run on every command execution
(ie, global config for the cli). That way, we don’t need to configure it within each CLI command.