[MERGE] Change CommitBuilder factory delegation to allow simple declaration.

[Aaron Bentley]

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Robert Collins wrote:
> On Fri, 2007-09-14 at 16:46 -0400, Aaron Bentley wrote:
>>> +        result = self.__class__._commit_builder_class(self, parents, config,
>>> +            timestamp, timezone, committer, revprops, revision_id)
>> I don't see why you're preventing overloading _commit_builder_class on
>> particular instances of Repository.  I think self._commit_builder_class
>> is more suitable.
>>
> 
> Our test suite only understands variation by format at the moment and
> every format has a dedicated class, so varying by instance does not
> assist us and could encourage the introduction of untested commit
> builders; I don't want to encourage that until/unless someone steps up
> with a use for it - and the changes (whatever they may be) to get it
> tested.

In Python, instance variables can override class variables, and as far
as I can tell, this is by design.  If this is a real concern of yours,
you haven't gone nearly far enough to prevent it.  For starters, commit
would need to do

self.builder = self.branch.__class__.get_commit_builder(self.branch ...

instead of

self.builder = self.branch.get_commit_builder(

Because methods are variables, too.  Your code doesn't look safer to me
in any meaningful way.  It looks like an arbitrary, ugly, violation of a
language feature.

Aaron
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