[MERGE][1.8?] Make 'bzr co' more memory sensitive

[Vincent Ladeuil]

>>>>> "john" == John Arbash Meinel <john at arbash-meinel.com> writes:

    john> Vincent Ladeuil wrote:
    john> ...

    john> +        """For the given keys, split them up based on their prefix.
    john> +
    john> +        To keep memory pressure somewhat under control, split the
    john> +        requests back into per-file-id requests, otherwise "bzr co"
    john> +        extracts the full tree into memory before writing it to disk.
    john> +        This should be revisited if _get_content_maps() can ever cross
    john> +        file-id boundaries.
    >> 
    >> Can you write a test guarding from regression on that particular
    >> case ?
    >> 
    >> BB:tweak
    >> 
    >> Convert that to approve from me if the test above is really too
    >> hard to get right, but in that case, add a FIXME.

    john> I don't really know how to write a correct test (that
    john> maximum memory is constrained).

I meant regression on "_get_content_maps() can ever cross file-id
boundaries.".

        Vincent