This will only take effect if PORTSDIR is not set, as previously supported.
Use .if exists(), for four specific possibilities relative to .CURDIR:
., .., ../.., and ../../.. The fourth possibility is primarily in case
ports ever grows a third level. If none of these paths exist, fall back to
the old default of /usr/ports.
This removes the need to set PORTSDIR explicitly (or via wrapper script) if
one is running out of a ports tree that is not in /usr/ports, but in a
home directory.
Reviewed by: bapt, bdrewery (older version)
CR: D799
MFC after: 1 week
Sponsored by: Spectra Logic
57c53dc77d