Support configuration defined ignore lists in a similar way as ESLint (loading ignore lists from multiple sources)

[Standard8]

The current options for ignoring files are inadequate for complex projects where lists of files to be ignored may be shared across different tools.

As proposed elsewhere in a PR, using ESLint's style of ignorePatterns in the configuration file would fix this issue and provide plenty of flexibility.

Using the same ignorePatterns in Prettier's configuration file would:

• Allow dynamically loading ignore files from other places.
• Allow the ignore list to be applied at the command line and in editors.
• Provide a single place for configuration.

The current options are inadequate because:

• Using .prettierignore does not allow import from other files.
• Using multiple --ignore-path arguments on the command line (added in v3), is not practical for editor integration, since different editors would need additional settings.
• prettierIgnore key in package.json? #3460 / Add support for prettierIgnore key in package.json #12672 are proposing for a prettierIgnore in package.json, however, this is insufficient as:
  • if you also used ESLint, then you'd have an eslintIgnore list as well which would likely largely be a duplicate.
  • you would not be able to load other ignore lists as package.json is a static file.

[Standard8]

Note, I originally attempted this here, but never got any feedback from the questions that I had raised about it.

[Standard8]

FTR #14785 seems to be the current proposal to implement this, although #15322 is an alternative.