Bring some OOP and sanity to gclient.py.

Bring some OOP and sanity to gclient.py.

- Changed the algorithm from breadth-first to depth-first.
- Added infinite recursion support.
- Fixed From() of From() dependency.
- Fixed cross solution custom deps aliasing.
- Removed support code for old .gclient_entries format.
- Removed IsGitCheckout() in favor for a direct check for .git presence.

TEST=all test pass

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=51760

[M-A Ruel, 2010-07-05 17:37:46]

Dependent on http://codereview.chromium.org/2885021/show

The main difference with http://codereview.chromium.org/2627007/show is that
gclient revinfo prints out exactly the same output as before.

gclient revinfo with From() dependencies is still broken in revinfo but this
will be changed in a later checkin as it was broken before and I'll add a smoke
test. As a result, gclient_smoke.py is mostly unmodifed except for the fix that
occured as a result of better granularity with which hooks are run in presence
of git checkout.

[Mandeep Singh Baines, 2010-07-07 17:00:09]

Just one minor nit.

http://codereview.chromium.org/2867047/diff/5001/6001
File gclient.py (right):

http://codereview.chromium.org/2867047/diff/5001/6001#newcode366
gclient.py:366: self.file_list[i] = self.file_list[i][1:]
Don't you want to strip 2 chars for the '\\' case.

[M-A Ruel, 2010-07-07 18:54:33]

http://codereview.chromium.org/2867047/diff/5001/6001
File gclient.py (right):

http://codereview.chromium.org/2867047/diff/5001/6001#newcode366
gclient.py:366: self.file_list[i] = self.file_list[i][1:]
On 2010/07/07 17:00:09, Mandeep Singh Baines wrote:
> Don't you want to strip 2 chars for the '\\' case.

It's the code around 663 in the previous version that was moved here but you
made me realize I had changed it slightly so I reverted to the previous code and
upload the fixed version.

I agree this will need to be fixed someday, it should always be relative paths.

[Mandeep Singh Baines, 2010-07-07 19:26:45]

LGTM