feat/issue-1398: added support for custom configuration

[RohitLuthra19]

Fixture for #1398

By proposed changes user will get the opportunity to control/handle the execution of custom task, As you can see in following example .lintstagedrc.js.

async function doFoo(files) {
  const { execa } = await import("execa");
  const result = await execa("eslint", [...files],
  {
    preferLocal: true,
    reject: false,
    shell: false,
    stdin: 'ignore'
  });
  if (result.failed || result.killed || result.signal != null) {
    throw result
  }
}

module.exports = {
  "**/*.{js,jsx}": (filenames) => {
    return {
      title: "Running a custom task",
      command: "Running a custom task",
      task: async () =>  {
        console.time()
        await doFoo(filenames)
        console.timeEnd()
      }
    }
  },
};

Following will be the output in case of no-console eslint error

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[grenganathan18]

Can we flip the condition and do an early return?

[RohitLuthra19]

done

[grenganathan18]

can we provide a meaningful error message on what specifically was the problem?

[RohitLuthra19]

done

[iiroj]

Do we need both the command and title?

[RohitLuthra19]

I think we only need title, so removed the command field.

[iiroj]

This file has started to become a bit complex... I wonder if we could split it somehow, maybe different handling for function and regular config.

[RohitLuthra19]

done

[iiroj]

We should add both unit and integration tests for this.

[iiroj]

Hey, please don't add versioning commits directly to the PR! It's automated in the GitHub Actions! I'm still thinking about this feature, there's no rush to get this in.

[RohitLuthra19]

iiroj I have incorporated all the review comments, you can proceed with the review/approval.

[iiroj]

While I appreciate your contribution, I don't think this feature is yet ready to be shipped with lint-staged and I want to spend some time thinking about it. For now I'll leave this PR open and use it as a base when I'm satisfied with the solution.

I also want to think about deprecating the --shell mode because it has security issues and using this method is more powerful anyway.

[iiroj]

After thinking about this, I like the feature but also realized that we can probably simplify the config by one level without it being a breaking change:

export default {
    "**/*.{js,jsx}": {
        title: "Running a custom task",
        task: async (filenames) =>  {
            console.time()
            await doFoo(filenames)
            console.timeEnd()
        }
    },
}

With this method the config looks like:

type Task = string

type CreateTask = (filenames: string[]) => Task | Task[] | Promise<Task | Task[]>

type FunctionTask = {
  title: string
  task: (filenames: string) => void | Promise<void>
}

type Configuration = Record<string, Task | Task[] | CreateTask | FunctionTask>

Unless I'm mistaken... what do you think? After this change we should just add some integration tests with a real config.