1.22.2.4

find-prefix.js
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			// try to find the most reasonable prefix to use

			module.exports = findPrefix

			var fs = require('fs')
			var path = require('path')

			function findPrefix (p, cb_) {
			function cb (er, p) {
			process.nextTick(function () {
			cb_(er, p)
			})
			}

			p = path.resolve(p)
			// if there's no node_modules folder, then
			// walk up until we hopefully find one.
			// if none anywhere, then use cwd.
			var walkedUp = false
			while (path.basename(p) === 'node_modules') {
			p = path.dirname(p)
			walkedUp = true
			}
			if (walkedUp) return cb(null, p)

			findPrefix_(p, p, cb)
			}

			function findPrefix_ (p, original, cb) {
			if (p === '/' \|\|
			(process.platform === 'win32' && p.match(/^[a-zA-Z]:(\\\|\/)?$/))) {
			return cb(null, original)
			}
			fs.readdir(p, function (er, files) {
			// an error right away is a bad sign.
			// unless the prefix was simply a non
			// existent directory.
			if (er && p === original) {
			if (er.code === 'ENOENT') return cb(null, original)
			return cb(er)
			}

			// walked up too high or something.
			if (er) return cb(null, original)

			if (files.indexOf('node_modules') !== -1 \|\|
			files.indexOf('package.json') !== -1) {
			return cb(null, p)
			}

			var d = path.dirname(p)
			if (d === p) return cb(null, original)

			return findPrefix_(d, original, cb)
			})
			}