packages/@vuepress/core/lib/node/dev/index.js
function normalizeWatchFilePath (filepath, baseDir) {
  const { isAbsolute, relative } = require('path')
  if (isAbsolute(filepath)) {
    return relative(baseDir, filepath)
  }
  return filepath
}
function normalizeWatchFilePath (filepath, baseDir) {
  const { isAbsolute, relative } = require('path')
  if (isAbsolute(filepath)) {
    return relative(baseDir, filepath)
  }
  return filepath
}
function normalizeWatchFilePath ( filepath , baseDir ) { const { isAbsolute , relative } = require ( 'path' ) if ( isAbsolute ( filepath ) ) { return relative ( baseDir , filepath ) } return filepath }
Normalize file path and always return relative path,

@param {string} filepath user's path
@param {string} baseDir source directory
@returns {string}
Normalize file path and always return relative path