Incorporate a search mechanism for PORTSDIR.

[will]

Summary

Instead of requiring the user to specify where their ports tree root is,
search for Mk/bsd.port.mk starting from the current directory. This will
still default to /usr/ports, and allow the user to override.

Test Plan

Apply diff, use a ports tree not in /usr/ports without specifying PORTSDIR,
and see that the correct Mk files are used. Also test the previously
supported cases, they should not be affected.

[bapt]

The same should be applied to bsd.port.subdir.mk

[will]

Version with bsd.port.subdir.mk also adjusted.

[will]

I could change this to use make conditionals instead and to explicitly check only .. and ../.. since those are the only reasonable cases really supported by ports right now.

[bdrewery]

Here's a simpler one with less subshells: http://people.freebsd.org/~bdrewery/patches/auto-portsdir2.txt

[bdrewery]

share/mk/bsd.port.mk

5

At least use $${PWD} here.

[bdrewery]

share/mk/bsd.port.mk

7

Perhaps to avoid POLA this should say "Using $$curdir for PORTSDIR" to stderr.

[will]

Updated version that doesn't use a shell callout.

This will only search up 2 levels at most. It also (on top of my comment)
searches the current directory, which is required because ports/Makefile
includes <bsd.port.subdir.mk>.

Tested both with and without an existing /usr/ports.

[will]

Updated with a comment and ../../.. check in case ports grows a third level.

[will]

Committed in r272282.