1#!/usr/bin/env python
2
3from __future__ import print_function
4
5import os
6import sys
7
8# Find the best reverse path to reference the current directory from another
9# directory. We use this to find relative paths to and from the source and build
10# directories.
11#
12# If the directory is given as an absolute path, return an absolute path to the
13# current directory.
14#
15# If there's a symlink involved, and the same relative path would not work if
16# the symlink was replace with a regular directory, then return an absolute
17# path. This handles paths like out -> /mnt/ssd/out
18#
19# For symlinks that can use the same relative path (out -> out.1), just return
20# the relative path. That way out.1 can be renamed as long as the symlink is
21# updated.
22#
23# For everything else, just return the relative path. That allows the source and
24# output directories to be moved as long as they stay in the same position
25# relative to each other.
26def reverse_path(path):
27    if path.startswith("/"):
28        return os.path.abspath('.')
29
30    realpath = os.path.relpath(os.path.realpath('.'), os.path.realpath(path))
31    relpath = os.path.relpath('.', path)
32
33    if realpath != relpath:
34        return os.path.abspath('.')
35
36    return relpath
37
38
39if __name__ == '__main__':
40    print(reverse_path(sys.argv[1]))
41