[PATCH remotefilelog-ext] fileserverclient: avoid ever requesting nullid nodes

[Augie Fackler]

> On Oct 24, 2016, at 19:06, Jun Wu <quark at fb.com> wrote:
> 
> Other than "len(nullids)", the patch looks good to me. I think we can fix it
> in flight.
> 
> Excerpts from Augie Fackler's message of 2016-10-24 18:44:31 -0400:
>> # HG changeset patch
>> # User Augie Fackler <augie at google.com>
>> # Date 1477347305 14400
>> #      Mon Oct 24 18:15:05 2016 -0400
>> # Node ID c282b94ef20c036ac6d68eca5ce07077eb61fcb9
>> # Parent  be571104d9f7292cd218dbb1aaebda9ac0b6315f
>> fileserverclient: avoid ever requesting nullid nodes
>> 
>> I keep tripping over bugs where this angers some part of our
>> stack. It's dumb to even be fetching these, but it's harmless to skip
>> them, so issue a developer warning when we encounter one and refuse to
>> fetch it.
>> 
>> diff --git a/remotefilelog/fileserverclient.py b/remotefilelog/fileserverclient.py
>> --- a/remotefilelog/fileserverclient.py
>> +++ b/remotefilelog/fileserverclient.py
>> @@ -577,6 +577,15 @@ class fileserverclient(object):
>>         if fetchhistory:
>>             missingids.update(historystore.getmissing(idstocheck))
>> 
>> +        # partition missing nodes into nullid and not-nullid so we can
>> +        # warn about this filtering potentially shadowing bugs.
>> +        nullids = len([None for unused, id in missingids if id == node.nullid])
>> +        if nullids:
>> +            missingids = [(f, id) for f, id in missingids if id != node.nullid]
>> +            repo.ui.develwarn(
>> +                ('remotefilelog not fetching %d null revs'
>> +                 ' - this is likely hiding bugs' % len(nullids)),
>                                                      ~~~~~~~~~~~~
>                                                 probably just "null ids"

Ugh, yep, good catch. I'll mail a v2 for ease of application.

>> +                config='remotefilelog-ext')
>>         if missingids:
>>             global fetches, fetched, fetchcost
>>             fetches += 1