Re: [PATCH] upload-pack: clear flags before each v2 request

>
> Suppose a server has the following commit graph:
>
>  A   B
>   \ /
>    O
>
> We create a client by cloning A from the server with depth 1, and add
> many commits to it (so that future fetches span multiple requests due to
> lengthy negotiation). If it then fetches B using protocol v2, the fetch
> spanning multiple requests, the resulting packfile does not contain O
> even though the client did report that A is shallow.
>
> This is because upload_pack_v2() can be called multiple times while
> processing the same session. During the 2nd and all subsequent
> invocations, some object flags remain from the previous invocations. In
> particular, CLIENT_SHALLOW remains, preventing process_shallow() from
> adding client-reported shallows to the "shallows" array, and hence
> pack-objects not knowing about these client-reported shallows.
>
> Therefore, teach upload_pack_v2() to clear object flags at the start of
> each invocation.
>
> (One alternative is to reduce or eliminate usage of object flags in
> protocol v2, but that doesn't seem feasible because almost all 8 flags
> are used pervasively in v2 code.)
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
> This was noticed by Arturas Moskvinas <arturas@uber.com> in [1]. The
> reproduction steps given were to repeat a shallow fetch twice in
> succession, but I found it easier to write a more understandable test if
> I made the 2nd fetch an ordinary fetch. In any case, I also reran the
> original reproduction steps, and the fetch completes without error.
>
> This patch doesn't cover the negotiation issue that I mentioned in my
> previous reply [2].
>
> [1] https://public-inbox.org/git/CAGY-PBgsG-T3JY=awszwGMpFx+jDx-a1FcV0s6vR067bSqgZaA@mail.gmail.com/
> [2] https://public-inbox.org/git/20181013004356.257709-1-jonathantanmy@google.com/
> ---
>  t/t5702-protocol-v2.sh | 25 +++++++++++++++++++++++++
>  upload-pack.c          |  5 +++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
> index 88a886975d..70b88385ba 100755
> --- a/t/t5702-protocol-v2.sh
> +++ b/t/t5702-protocol-v2.sh
> @@ -429,6 +429,31 @@ test_expect_success 'fetch supports include-tag and tag following' '
>         git -C client cat-file -e $(git -C client rev-parse annotated_tag)
>  '
>
> +test_expect_success 'upload-pack respects client shallows' '
> +       rm -rf server client trace &&
> +
> +       git init server &&
> +       test_commit -C server base &&
> +       test_commit -C server client_has &&
> +
> +       git clone --depth=1 "file://$(pwd)/server" client &&
> +
> +       # Add extra commits to the client so that the whole fetch takes more
> +       # than 1 request (due to negotiation)
> +       for i in $(seq 1 32)
> +       do
> +               test_commit -C client c$i
> +       done &&
> +
> +       git -C server checkout -b newbranch base &&
> +       test_commit -C server client_wants &&
> +
> +       GIT_TRACE_PACKET="$(pwd)/trace" git -C client -c protocol.version=2 \
> +               fetch origin newbranch &&
> +       # Ensure that protocol v2 is used
> +       grep "git< version 2" trace
> +'
> +
>  # Test protocol v2 with 'http://' transport
>  #
>  . "$TEST_DIRECTORY"/lib-httpd.sh
> diff --git a/upload-pack.c b/upload-pack.c
> index 62a1000f44..de7de1de38 100644
> --- a/upload-pack.c
> +++ b/upload-pack.c
> @@ -37,6 +37,9 @@
>  #define CLIENT_SHALLOW (1u << 18)
>  #define HIDDEN_REF     (1u << 19)
>
> +#define ALL_FLAGS (THEY_HAVE | OUR_REF | WANTED | COMMON_KNOWN | SHALLOW | \
> +               NOT_SHALLOW | CLIENT_SHALLOW | HIDDEN_REF)
> +
>  static timestamp_t oldest_have;
>
>  static int deepen_relative;
> @@ -1393,6 +1396,8 @@ int upload_pack_v2(struct repository *r, struct argv_array *keys,
>         enum fetch_state state = FETCH_PROCESS_ARGS;
>         struct upload_pack_data data;
>
> +       clear_object_flags(ALL_FLAGS);
> +
>         git_config(upload_pack_config, NULL);
>
>         upload_pack_data_init(&data);
> --
> 2.19.0.271.gfe8321ec05.dirty
>