Add support for "fix" option to config file

[baolsen]

Summary

tflint recently added a --fix CLI application parameter.

Support for the same thing should be added to the .tflint.hcl config file, for consistency.

I prefer to have a single way to configure the application, but at the moment I need to provide both a config file as well as flags.

Here is an example of how it might look.

config {
  fix = true
}

[bendrucker]

https://golangci-lint.run/docs/configuration/file/
https://eslint.org/docs/latest/use/configure/configuration-files

Prior art is mixed. ESLint exposes fixes via CLI options only, while golangci-lint supports a config file parameter.

for consistency.

This can cause problems if applied to all inputs.

Flags can only be specified once per CLI invocation. Config can be module-level, leading to hacky behaviors like this:

https://github.com/terraform-linters/tflint/blob/master/docs/user-guide/config.md#format

In recursive mode (--recursive), this field will be ignored in configuration files and must be set via a flag.

Unlike format, which has to be consistent across a run, in theory, it would be okay to have conflicting fix settings in a recursive run as long as they were respected on a per-module level.

If you agree that when recursing, modules should be able to opt in and out of auto-fix, that should avoid the format issue.

Separately, if you can set fix via config, we might also want a flag to allow users to override that at call time. --fix overrides fix = false, but also --no-fix overrides fix = true.

[wata727]

Personally, I'm not a fan of having --fix implicitly enabled by config file, as it has side effects.
I expect that the issue of implicit side effects will probably be greater than the inconsistency.