[MERGE] Support fetching a restricted set of revisions

[Ian Clatworthy]

Aaron Bentley wrote:
> Ian Clatworthy wrote:
>> Jelmer Vernooij wrote:
>> Exciting to see some progress on this feature!
> 
>> I appreciate this isn't exposed at the UI yet and the direction you're
>> going has precedence with the --depth option of git clone, but are we
>> sure we want to control depth via a numeric limit?
> 
> I don't think he's indicated that he's going with --depth.  In fact,
> Robert's wrap-up message said "Jelmer has 'branch -r -5.. working"

Cool. Thanks for the reminder.

The lower level code was talking about a limit in terms of size instead
of an origin revision though. Starting with a limit and generalising
after that is great as long as the latter happens (and the lower level
APIs are private in the meantime).

Ian C.