Implements the node require.resolve() algorithm except you can pass in the file to compute paths relatively to along with your own require.paths without updating the global copy (which doesn't even work in node >=0.5).

var resolve = require('resolve');

Synchronously search for the package/filename string pkg according to the require.resolve() algorithm for X=pkg and Y=opts.basedir.

Default values for opts:

{
    paths : [],
    basedir : __dirname,
    extensions : [ '.js' ],
    readFileSync : fs.readFileSync,
    isFile : function (file) {
        return path.existSync(file) && fs.statSync(file).isFile()
    }
}

Optionally you can specify a opts.packageFilter function to map the contents of JSON.parse()'d package.json files.

If nothing is found, all of the directories in opts.paths are searched.

Return whether a package is in core.