support function-type options.ignore

[kaelzhang]

Is it possible for node-glob to support function-type options.ignore ?

Case

If we want to list all files according to the .gitignore, and the .gitignore file is:

node_modules/*
!node_modules/dir-to-be-included/

Suppose there are thousands of things inside node_modules, we should filter out those useless directories at the certain stage of glob and not after globbing, or the matching process of glob will be very slow.

But it is not that easy to use glob pattern to imitate the behavior of gitignore.

Proposal

glob('**/*', {
  ignore: function(path){
     return whetherShouldIgnoreByGitignore(path) 
     // Pay attention that gitignore patterns are not glob patterns
  }
}, (err, files) => {
  doThingsWith(files)
})

[kaelzhang]

If it is ok to do this, I can help with pr.

[kaelzhang]

@isaacs May I have any suggestions?

[isaacs]

This is a good feature request for v9, but supporting it on v8 was too terrible to consider.