[PATCH 0/2] receive-pack: use advertised reference tips to inform connectivity check

Hi,

this patch series improves the connectivity check done by stateful git-receive-pack(1) to only consider references as reachable that have been advertised to the client. This has two advantages:

    - A client shouldn't assume objects to exist that have not been part
      of the reference advertisement. But if it excluded an object from
      the packfile that is reachable via any ref that is excluded from
      the reference advertisement due to `transfer.hideRefs` we'd have
      accepted the push anyway. I'd argue that this is a bug in the
      current implementation.

    - Second, by using advertised refs as inputs instead of `git
      rev-list --not --all` we avoid looking up all refs that are
      irrelevant to the current push. This can be a huge performance
      improvement in repos that have a huge amount of internal, hidden
      refs. In one of our repos with 7m refs, of which 6.8m are hidden,
      this speeds up pushes from ~30s to ~4.5s.

One downside is that we need to pass in the object IDs that were part of the reference advertisement via the standard input, which is seemingly slower than reading them from the refdb. I'm discussing this in the second commit.

Patrick

Patrick Steinhardt (2):
  connected: allow supplying different view of reachable objects
  receive-pack: use advertised reference tips to inform connectivity
    check

 builtin/receive-pack.c | 31 ++++++++++++++++++++++---------
 connected.c            |  9 ++++++++-
 connected.h            |  7 +++++++
 3 files changed, 37 insertions(+), 10 deletions(-)