Junctions are sometimes used as links (e.g. mklink /j) and sometimes as volume mount points (e.g. mountvol.exe). GetVolumePathName can be called to distinguish these cases. If a junction is a volume mount point, then its absolute path and volume path are the same. This test is already used in ntpath.ismount().

For a junction link, islink() should return true, readlink() should work, and S_ISDIR() should return false for the lstat() st_mode. For a junction mount point, islink() should return false, readlink() should not work, and S_ISDIR() should return true for the lstat() st_mode.

A helper function could be added in fileutils.c to determine whether a reparse point is a link, based on the file path and reparse tag. Then modify _Py_attribute_data_to_stat() to take `BOOL is_link` instead of `ULONG reparse_tag`.