Reapply 48271 with fix (again)

Reapply 48271 for the third time with fix.

"""
Enable automatic command and one-liner doc. Reformat pydoc accordingly.
Add parser as an argument and parse_args hook in preparation to move parse_args at the right place, inside the CMDxx functions.

R.I.P. gclient_test.py
"""
original code review at: http://codereview.chromium.org/2253002

In addition:
- Add more smoke tests: vars, hooks, runhooks
- Bugs filed about misbehavior with git checkout
- Fixed gclient runhooks

TEST=smoke test
BUG=23328
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=48309

[M-A Ruel, 2010-05-26 15:50:11]

Please take a look at this review, I plan to add more smoke test with important
steps, e.g. the one run on the continuous build and try server. I'm trying to
get this in to fix a P0: http://crosbug.com/3465

[Mandeep Singh Baines, 2010-05-26 17:43:08]

Nice cleanup. LGTM

[M-A Ruel, 2010-05-26 18:49:32]

I had to revert because of an exception with runhooks. I added the corresponding
options.deps_os = None and a regression test. I reused the same review so you
could see the differences.

[msb, 2010-05-26 19:00:49]

LGTM

maruel@chromium.org (maruel@chromium.org) wrote:
> I had to revert because of an exception with runhooks. I added the  
> corresponding
> options.deps_os = None and a regression test. I reused the same review so 
> you
> could see the differences.
>
> http://codereview.chromium.org/2265002/show