Rework the owner-suggesting algorithm.

Rework the owner-suggesting algorithm.

It turns out that we were weighting all possible owners equally,
and picking the last one out of the list. Given the way we traversed
owners files, and given that we got rid of the "set noparent"s, this
meant that we were always suggesting Ben for just about everything.

This change implements a much smarter algorithm that attempts to balance
number of reviewers and closeness to the files under review. The unit
tests added show specific examples and explanations for why things are
chosen the way they are.

R=maruel@chromium.org
BUG=76727
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=173784

[M-A Ruel, 2012-12-17 22:27:18]

lgtm with nits.

https://codereview.chromium.org/11567052/diff/3001/owners.py
File owners.py (right):

https://codereview.chromium.org/11567052/diff/3001/owners.py#newcode268
owners.py:268: # This returns a list of (potential owner, distance-from-dir)
tuples;
Should be a docstring.

https://codereview.chromium.org/11567052/diff/3001/owners.py#newcode305
owners.py:305: lowest_cost = min(total_costs_by_owner.values())
itervalues()

https://codereview.chromium.org/11567052/diff/3001/tests/owners_unittest.py
File tests/owners_unittest.py (right):

https://codereview.chromium.org/11567052/diff/3001/tests/owners_unittest.py#n...
tests/owners_unittest.py:210: 
remove extra line

[Dirk Pranke, 2012-12-18 21:13:21]

https://codereview.chromium.org/11567052/diff/3001/owners.py
File owners.py (right):

https://codereview.chromium.org/11567052/diff/3001/owners.py#newcode268
owners.py:268: # This returns a list of (potential owner, distance-from-dir)
tuples;
On 2012/12/17 22:27:19, Marc-Antoine Ruel wrote:
> Should be a docstring.

Done.

https://codereview.chromium.org/11567052/diff/3001/owners.py#newcode305
owners.py:305: lowest_cost = min(total_costs_by_owner.values())
On 2012/12/17 22:27:19, Marc-Antoine Ruel wrote:
> itervalues()

Done. As an FYI, itervalues() goes away in python 3, and I doubt there's much of
a difference for short lists like this either way ...

[commit-bot: I haz the power, 2012-12-18 21:16:07]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dpranke@chromium.org/11567052/6001

[commit-bot: I haz the power, 2012-12-18 21:18:51]

Change committed as 173784