Better CLI

[okonet]

What kind of change does this PR introduce?
feature / refactoring

Did you add tests for your changes?

No, we need to introduce e2e tests for that

If relevant, did you update the documentation?

Yes

Summary

Refactors the CLI code so we use commands for migrate and init.
Made use of yargs to simplify the source code.
Consolidated all webpack options into one file.

Does this PR introduce a breaking change?
Yes, the commands should be now called with webpack-cli migrate instead of webpack-cli --migrate

Other information

[evenstensberg]

Ready for review @okonet ?

[okonet]

Almost there.

[okonet]

So after spending a good amount of time on this, I reached a dead end it seems. I can't think of a good way of doing this change as a non-breaking change to the existing webpack CLI.

The problem is that current CLI syntax looks like this webpack <entry> [<entry>] <output>.

Making migrate and init tasks act as commands means, the syntax to use them will be webpack init which might be ambiguous to the current webpack CLI.

Another issue I tried to solve is to not display all options by default when running webpack --help. This also seems impossible with a non-breaking change.

A breaking change means an introduction of an additional command for webpack default behavior. For example compile or start.

There is probably a solution for this that involves parsing of arguments but I'm not sure yet how reliable this can be implemented. Any feedback is appreciated!

@sokra I think you should be involved in this discussion since implications can be pretty big.

[TheLarkInn]

Any good ideas @sokra

[okonet]

We discussed on Slack but I'm a bit drawn by work now so I'll continue on this in a week or so.

[pksjce]

This should point to new docs?

[DanielaValero]

@okonet anything here for me to help with?

[okonet]

More free time would be great :( Seriously though, having tests would help dramatically before I refactor even further. Not sure how much of this is covered.

[evenstensberg]

@okonet we should get that react test suite up and running first, yea?

[okonet]

What react test suit? You mean Jest snapshot tests? yes, that would be great to have. We need 100% coverage if we don't want break current implementation.

[evenstensberg]

@okonet You mentioned on Slack that instead of Soren, you could use this https://github.com/vadimdemedes/ink for testing

[okonet]

@ev1stensberg it's not for testing but for the CLI itself and I'd like to look into it.

[evenstensberg]

@okonet gotcha! We would need to come up with a way to test E2E and produce results, both for the new features but also the "old" CLI commands that webpack have.

[evenstensberg]

May be better to redo this in another fresh PR after its been merged with webpack, closing @okonet , reopen if you want to continue to work on this branch!