Add features flag to gmerge.

Add features flag to gmerge and some whitespace cleanup.

Change-Id: I95aec88a491b0aee08f100af72d608b326fcf9c4

BUG=chromium-os:13992
TEST=Ran sudo gmerge chromos-base/gmerge to update to latest gmerge and then
ran sudo gmerge --features=test chromeos-base/metrics and saw test phase
run on dev machine.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=dda923d

[rochberg, 2011-04-09 19:59:33]

http://codereview.chromium.org/6824021/diff/1/builder.py
File builder.py (right):

http://codereview.chromium.org/6824021/diff/1/builder.py#newcode63
builder.py:63: os.environ['FEATURES'] = original_use + ' ' +
additional_args['features']
= original_features + ...

Probably best to switch to making a full copy of os.environ and save this whole
mess. about original_*

http://codereview.chromium.org/6824021/diff/1/builder.py#newcode89
builder.py:89: os.environ['USE'] = original_use
Should also restore FEATURES, or, better yet, be more generic about the
environment restore.

http://codereview.chromium.org/6824021/diff/1/gmerge
File gmerge (right):

http://codereview.chromium.org/6824021/diff/1/gmerge#newcode107
gmerge:107: dest='features', default=None,
Feel free to say "another CL" or "No U", but I think we should also look at the
host environment here.  Despite having written the --USE= stuff, I still find
myself typing USE=foo gmerge .... and then being surprised when my USE flags
don't go through.

[sosa, 2011-04-13 20:04:08]

Took all your suggestions.  PTAL

http://codereview.chromium.org/6824021/diff/5001/gmerge
File gmerge (right):

http://codereview.chromium.org/6824021/diff/5001/gmerge#newcode123
gmerge:123: merger.SetupPortageEnvironment(os.environ)
Move down to not affect environment passed to build.

[rochberg, 2011-04-13 20:10:59]

LGTM.
And that's totally the right way to do the env.