Function relative

packages/angular_devkit/core/src/virtual-fs/path.ts:129–161

(from: Path, to: Path)

 * Both paths must be absolute, otherwise it does not make much sense.
 */
export function relative(from: Path, to: Path): Path {
  if (!isAbsolute(from)) {
    throw new PathMustBeAbsoluteException(from);
  }
  if (!isAbsolute(to)) {
    throw new PathMustBeAbsoluteException(to);
  }

  let p: string;

  if (from == to) {
    p = '';
  } else {
    const splitFrom = split(from);
    const splitTo = split(to);

    while (splitFrom.length > 0 && splitTo.length > 0 && splitFrom[0] == splitTo[0]) {
      splitFrom.shift();
      splitTo.shift();
    }

    if (splitFrom.length == 0) {
      p = splitTo.join(NormalizedSep);
    } else {
      p = splitFrom
        .map(() => '..')
        .concat(splitTo)
        .join(NormalizedSep);
    }
  }

  return normalize(p);
}

/**
 * Returns a Path that is the resolution of p2, from p1. If p2 is absolute, it will return p2,