tree a371ea53349d73c45e3f65d79b76872ebd28d861
parent a661e2e9eb51bbabec4682345bc0c9b002e32578
author Ivan Frade <ifrade@google.com> 1586208952 -0700
committer Ivan Frade <ifrade@google.com> 1588139079 -0700

UploadPack: Use more relevant refs first in object reachability check

The bitmap-bassed object reachability checker, tries to find the objects
in the first starter, then adding the second starter... and so on. This
rewards passing the most popular refs first.

Order the refs with heads first, then tags, then others (e.g. changes)
for the object reachability checker. Using streams, delay also the
resolution of the ref to RevObject until necessary.

Change-Id: I9414b76754d7c0ffee1e2eeed6939895c8e92cbe
Signed-off-by: Ivan Frade <ifrade@google.com>