function toRelativeSourcePath(fullPath, rootPath) {
  return toPosixPath(fullPath).replace(toPosixPath(rootPath), '.');
}
Simple helper te make code a bit more readable.
- from '/path/to/repo/my/file.js';
- to './my/file.js'
@param {string} fullPath like '/path/to/repo/my/file.js'
@param {string} rootPath like '/path/to/repo'