fix: 🐛 defaults flag behaviour

[anshumanv]

✅ Closes: #1322

What kind of change does this PR introduce?
Fix the application of default flags

Did you add tests for your changes?
Yes, enabled

If relevant, did you update the documentation?
Not needed

Summary

• Fix the bug in the approach we use webpack-merge to apply default config.

Does this PR introduce a breaking change?
No.

Other information

[webpack-bot]

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[rishabh3112]

Looks good to me. Thanks!

[snitin315]

@anshumanv can you resolve conflicts?

[anshumanv]

Do we wish to support this @webpack/cli-team?

[alexander-akait]

@anshumanv we need investigate what does this option do, most likely we will remove it

[anshumanv]

@evilebottnawi when passed, default config is merged with the supplied config by the user https://github.com/webpack/webpack-cli/blob/dfb9a9142706751617eb38dc9f3e00f8ec750ec9/packages/webpack-cli/lib/utils/development-config.js or https://github.com/webpack/webpack-cli/blob/dfb9a9142706751617eb38dc9f3e00f8ec750ec9/packages/webpack-cli/lib/utils/production-config.js

Not sure of the use case

[anshumanv]

Should we remove it then?

[alexander-akait]

Yes, no need, let's remove, webpack already has good default values

[anshumanv]

Okay, closing and removing in next PR. 👍