[PATCH 1 of 3 V2 STABLE] changelog: introduce count argument to revs() function

[Alexander Plavin]

2013/7/23 Alexander Plavin <me at aplavin.ru>:
> 2013/7/23 Brodie Rao <brodie at sf.io>:
>> On Mon, Jul 22, 2013 at 2:54 AM, Alexander Plavin <me at aplavin.ru> wrote:
>>> # HG changeset patch
>>> # User Alexander Plavin <me at aplavin.ru>
>>> # Date 1374321959 -14400
>>> #      Sat Jul 20 16:05:59 2013 +0400
>>> # Node ID 82096c966790ec607efb16ebff2cfa53c643b700
>>> # Parent  b97ce93726dbcbfc439458e244a266953c22940e
>>> changelog: introduce count argument to revs() function
>>>
>>> This allows specifying count of revisions to yield, which is convenient when
>>> some revs are filtered.
>>>
>>> diff -r b97ce93726db -r 82096c966790 mercurial/changelog.py
>>> --- a/mercurial/changelog.py    Fri Jul 19 21:26:08 2013 +0400
>>> +++ b/mercurial/changelog.py    Sat Jul 20 16:05:59 2013 +0400
>>> @@ -147,11 +147,23 @@
>>>
>>>          return filterediter()
>>>
>>> -    def revs(self, start=0, stop=None):
>>> +    def revs(self, start=0, stop=None, count=None):
>>>          """filtered version of revlog.revs"""
>>> +        if count is not None:
>>> +            if count < 0:
>>> +                stop = 0
>>> +            elif count > 0:
>>> +                stop = len(self)
>>> +            else:
>>> +                stop = start
>>> +
>>> +        curcount = 0
>>>          for i in super(changelog, self).revs(start, stop):
>>>              if i not in self.filteredrevs:
>>>                  yield i
>>> +                curcount += 1
>>> +                if count is not None and curcount >= abs(count):
>>> +                    break
>>
>> Instead of making this change inside changelog.revs(), couldn't you
>> use itertools.islice() where you need to limit the number of
>> revisions?
>
> I thought about such variant, but this one (from this patch) seemed
> more convenient to use in the calling place and more universal.
> ('revs(start, -count)' vs 'itertools.islice(revs(start, 0), count)').
> If anyone else agrees that with islice it will be better, I will
> change and resend.

Also, (forgot to add to the previous message) it relies on the
function returning an iterator, but not a list of requested revisions
and uses this knowledge (if it was returning list,
'itertools.islice(revs(start, 0), count)' would be very inefficient).

>
>>
>>>      @util.propertycache
>>>      def nodemap(self):
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