On 4/8/21 9:10 PM, Jonathan Tan wrote:
> Teach Git the push.negotiate config variable.
...
> +push.negotiate::
> + If set to "true", attempt to reduce the size of the packfile
> + sent by rounds of negotiation in which the client and the
> + server attempt to find commits in common. If "false", Git will
> + rely solely on the server's ref advertisement to find commits
> + in common.
Works for me.
> diff --git a/send-pack.c b/send-pack.c
> index 5f215b13c7..9cb9f71650 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -56,7 +56,9 @@ static void feed_object(const struct object_id *oid, FILE *fh, int negative)
> /*
> * Make a pack stream and spit it out into file descriptor fd
> */
> -static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struct send_pack_args *args)
> +static int pack_objects(int fd, struct ref *refs, struct oid_array *advertised,
> + struct oid_array *negotiated,
> + struct send_pack_args *args)
At the moment, I don't see why we need two oid_arrays here.
Instead, this 'extra' could instead be renamed to something
like 'server_objects' or 'base_objects' to make it clear
that we don't want those objects, and can even use them and
their reachable objects as delta bases, when appropriate.
Or, just don't touch it.
> +static void get_commons_through_negotiation(const char *url,
> + const struct ref *remote_refs,
> + struct oid_array *commons)
> +{
> + struct child_process child = CHILD_PROCESS_INIT;
> + const struct ref *ref;
> + int len = the_hash_algo->hexsz + 1; /* hash + NL */
> +
> + child.git_cmd = 1;
> + child.no_stdin = 1;
> + child.out = -1;
> + strvec_pushl(&child.args, "fetch", "--negotiate-only", NULL);
> + for (ref = remote_refs; ref; ref = ref->next)
> + strvec_pushf(&child.args, "--negotiation-tip=%s", oid_to_hex(&ref->new_oid));
> + strvec_push(&child.args, url);
Oh! We are using a 'git fetch --negotiate-only' subprocess here. You
can ignore my previous message about updating the docs for this to be
used only by tests.
> +
> + if (start_command(&child))
> + die(_("send-pack: unable to fork off fetch subprocess"));
> +
> + do {
> + char hex_hash[GIT_MAX_HEXSZ + 1];
> + int read_len = read_in_full(child.out, hex_hash, len);
> + struct object_id oid;
> + const char *end;
> +
> + if (!read_len)
> + break;
> + if (read_len != len)
> + die("invalid length read %d", read_len);
> + if (parse_oid_hex(hex_hash, &oid, &end) || *end != '\n')
> + die("invalid hash");
> + oid_array_append(commons, &oid);
This appends, so there is no reason why it needs to be empty before
the method. Is there a way we could feed the extra_have set when
calling this method? Or is it happening at a strange time?
> + } while (1);
> +
> + if (finish_command(&child)) {
> + /*
> + * The information that push negotiation provides is useful but
> + * not mandatory.
> + */
> + warning(_("push negotiation failed; proceeding anyway with push"));
> + }
> +}
> +
> int send_pack(struct send_pack_args *args,
> int fd[], struct child_process *conn,
> struct ref *remote_refs,
> struct oid_array *extra_have)
> {
> + struct oid_array commons = OID_ARRAY_INIT;
> int in = fd[0];
> int out = fd[1];
> struct strbuf req_buf = STRBUF_INIT;
> @@ -426,6 +474,7 @@ int send_pack(struct send_pack_args *args,
> int quiet_supported = 0;
> int agent_supported = 0;
> int advertise_sid = 0;
> + int push_negotiate = 0;
> int use_atomic = 0;
> int atomic_supported = 0;
> int use_push_options = 0;
> @@ -437,6 +486,10 @@ int send_pack(struct send_pack_args *args,
> const char *push_cert_nonce = NULL;
> struct packet_reader reader;
>
> + git_config_get_bool("push.negotiate", &push_negotiate);
> + if (push_negotiate)
> + get_commons_through_negotiation(args->url, remote_refs, &commons);
> +
> git_config_get_bool("transfer.advertisesid", &advertise_sid);
>
> /* Does the other end support the reporting? */
> @@ -625,7 +678,7 @@ int send_pack(struct send_pack_args *args,
> PACKET_READ_DIE_ON_ERR_PACKET);
>
> if (need_pack_data && cmds_sent) {
> - if (pack_objects(out, remote_refs, extra_have, args) < 0) {
> + if (pack_objects(out, remote_refs, extra_have, &commons, args) < 0) {
Here, it would be nice if extra_have and commons were merged before calling
pack_objects(). I mentioned a way to perhaps make that easier above, but
the context might not make that be super-simple. Running a loop here to
scan 'commons' and append them to 'extra_have' might be a sufficient
approach.
Generally, this approach seems like it would work. I have not done any
local testing, yet.
Thanks,
-Stolee
