[RFC PATCH 0/2] builtin/receive-pack: introduce option to skip connectivity checks

[Justin Tobler <jltobler@gmail.com>]

Greetings,

At GitLab, we are interested in introducing an optional means to bypass
the connectivity checks performed through git-receive-pack(1). This
series implements a `--skip-connectivity-check` option to facilitate
this. I'm interested in collecting some thoughts before pursuing further
though.

For some background, we have a transaction management system that runs
in our Git RPC service and wraps all repository operations. Operations
that write to a repository are first recorded and staged outside of the
repository. When committing a transaction, the connectivity of newly
written objects is checked by walking the object graph containing only
the new objects from the updated tips and identifying the missing
objects which represent the boundary between the new objects and the
repository. The boundary objects are then checked in the canonical
repository to ensure the new objects will connect as expected. All
repository operations are run in a transaction and conflict checked
before being applied serially to the canonical repository. This ensures
that operations that would break the repository are not applied.

For our specific use case, the conflict checks performed by
git-receive-pack(1) are redundant and thus we would like to introduce an
option that allows connectivity checks to be skipped.

One concern I see could be the `--receive-pack` flag for git-push(1) or
the `remote.<name>.receivepack` option which configures the receive-pack
program that gets executed on the remote side for some protocols. This
could provide a way for users to enable such a flag if the remote
doesn't protect against arbitrary arguments being added. I don't think
git-shell(1) would protect against this, so maybe instead of a flag a
config option could be used or an ENV var?

Thanks for taking a look.

-Justin

Justin Tobler (2):
  t5412: test receive-pack connectivity check
  builtin/receive-pack: add option to skip connectivity check

 builtin/receive-pack.c  | 40 +++++++++++++++++++----------------
 t/meson.build           |  1 +
 t/t5412-receive-pack.sh | 47 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 18 deletions(-)
 create mode 100755 t/t5412-receive-pack.sh


base-commit: 6c0bd1fc70efaf053abe4e57c976afdc72d15377
-- 
2.49.0.111.g5b97a56fa0