Re: [PATCH v3 3/3] object-info: add option for retrieving object info

[Calvin Wan <calvinwan@google.com>]

Thank you for the code hygiene tips, Taylor! All of these sounds like
good ideas and will follow through

On Tue, Mar 29, 2022 at 4:19 PM Taylor Blau <me@ttaylorr.com> wrote:
>
> Hi Calvin,
>
> Junio took a deeper look below, but here are a few small code-hygiene
> issues that I noticed while taking a quicker look through this patch.
>
> On Mon, Mar 28, 2022 at 07:11:12PM +0000, Calvin Wan wrote:
> > Sometimes it is useful to get information about an object without
> > having to download it completely. The server logic has already been
> > implemented as “a2ba162cda (object-info: support for retrieving object
> > info, 2021-04-20)”. This patch implements the client option for
> > it. Currently, only 'size' is supported, however future patches can
> > implement additional options.
> >
> > Add ‘--object-info’ option to fetch. This option allows the client to
>
> The single-quotes here look like smart quotes. I don't think we forbid
> these explicitly within commit messages, but using the standard '
> (ASCII 0x27) character is more common.
>
> > make an object-info command request to a server that supports protocol
> > v2. If the server is v2, but does not allow for the object-info
> > command request, fetch the objects as if it were a standard fetch
> > (however without changing any refs). Therefore, hook `fetch
> > object-info` into transport_fetch_refs() to easily fallback if needed.
> >
> > A previous patch added the `transfer.advertiseObjectInfo` config
> > option, of which this patch utilizes to test the fallback.
> >
> > ---
> >  Documentation/fetch-options.txt |   5 ++
> >  Documentation/git-fetch.txt     |   1 +
> >  builtin/fetch.c                 |  36 ++++++++-
> >  fetch-pack.c                    |  42 +++++++++-
> >  fetch-pack.h                    |   9 +++
> >  t/t5583-fetch-object-info.sh    | 138 ++++++++++++++++++++++++++++++++
> >  transport-helper.c              |   8 +-
> >  transport-internal.h            |   1 +
> >  transport.c                     |  75 ++++++++++++++++-
> >  transport.h                     |   9 +++
> >  10 files changed, 315 insertions(+), 9 deletions(-)
> >  create mode 100755 t/t5583-fetch-object-info.sh
> >
> > diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
> > index f903683189..f1ca95c32d 100644
> > --- a/Documentation/fetch-options.txt
> > +++ b/Documentation/fetch-options.txt
> > @@ -299,3 +299,8 @@ endif::git-pull[]
> >  -6::
> >  --ipv6::
> >       Use IPv6 addresses only, ignoring IPv4 addresses.
> > +
> > +--object-info=[<arguments>]::
> > +     Fetches only the relevant information passed in arguments from a
> > +     specific remote and set of object ids. Object 'size' is currently
> > +     the only supported argument.
> > diff --git a/Documentation/git-fetch.txt b/Documentation/git-fetch.txt
> > index 550c16ca61..a13d2ba7ad 100644
> > --- a/Documentation/git-fetch.txt
> > +++ b/Documentation/git-fetch.txt
> > @@ -13,6 +13,7 @@ SYNOPSIS
> >  'git fetch' [<options>] <group>
> >  'git fetch' --multiple [<options>] [(<repository> | <group>)...]
> >  'git fetch' --all [<options>]
> > +'git fetch' --object-info=[<arguments>] <remote> [<object-ids>]
> >
> >
> >  DESCRIPTION
> > diff --git a/builtin/fetch.c b/builtin/fetch.c
> > index 4d12c2fd4d..0b21bebfca 100644
> > --- a/builtin/fetch.c
> > +++ b/builtin/fetch.c
> > @@ -29,6 +29,9 @@
> >  #include "commit-graph.h"
> >  #include "shallow.h"
> >  #include "worktree.h"
> > +#include "protocol.h"
> > +#include "pkt-line.h"
> > +#include "connect.h"
> >
> >  #define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
> >
> > @@ -37,6 +40,7 @@ static const char * const builtin_fetch_usage[] = {
> >       N_("git fetch [<options>] <group>"),
> >       N_("git fetch --multiple [<options>] [(<repository> | <group>)...]"),
> >       N_("git fetch --all [<options>]"),
> > +     N_("git fetch --object-info=[<arguments>] <remote> [<object-ids>]"),
> >       NULL
> >  };
> >
> > @@ -86,6 +90,7 @@ static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
> >  static int fetch_write_commit_graph = -1;
> >  static int stdin_refspecs = 0;
> >  static int negotiate_only;
> > +static struct string_list object_info_options = STRING_LIST_INIT_NODUP;
> >
> >  static int git_fetch_config(const char *k, const char *v, void *cb)
> >  {
> > @@ -221,6 +226,8 @@ static struct option builtin_fetch_options[] = {
> >                N_("write the commit-graph after fetching")),
> >       OPT_BOOL(0, "stdin", &stdin_refspecs,
> >                N_("accept refspecs from stdin")),
> > +     OPT_STRING_LIST(0, "object-info", &object_info_options, N_("option"),
> > +              N_("command request arguments")),
> >       OPT_END()
> >  };
> >
> > @@ -2087,6 +2094,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
> >       struct remote *remote = NULL;
> >       int result = 0;
> >       int prune_tags_ok = 1;
> > +     struct oid_array object_info_oids = OID_ARRAY_INIT;
> >
> >       packet_trace_identity("fetch");
> >
> > @@ -2168,7 +2176,19 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
> >       if (dry_run)
> >               write_fetch_head = 0;
> >
> > -     if (all) {
> > +     if (object_info_options.nr > 0) {
>
> Small nit; since object_info_options.nr should never be negative, we
> should instead write "if (object_info_options)".
>
> > +             if (argc == 0 || argc == 1) {
> > +                     die(_("must supply remote and object ids when using --object-info"));
> > +             } else {
> > +                     struct object_id oid;
> > +                     remote = remote_get(argv[0]);
> > +                     for (i = 1; i < argc; i++) {
> > +                             if (get_oid(argv[i], &oid))
> > +                                     return error(_("malformed object id '%s'"), argv[i]);
> > +                             oid_array_append(&object_info_oids, &oid);
> > +                     }
> > +             }
> > +     } else if (all) {
> >               if (argc == 1)
> >                       die(_("fetch --all does not take a repository argument"));
> >               else if (argc > 1)
> > @@ -2199,7 +2219,19 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
> >               }
> >       }
> >
> > -     if (negotiate_only) {
> > +     if (object_info_options.nr > 0) {
> > +             if (!remote)
> > +                     die(_("must supply remote when using --object-info"));
> > +             gtransport = prepare_transport(remote, 1);
> > +             if (gtransport->smart_options) {
> > +                     gtransport->smart_options->object_info = 1;
> > +                     gtransport->smart_options->object_info_oids = &object_info_oids;
> > +                     gtransport->smart_options->object_info_options = &object_info_options;
> > +             }
> > +             if (server_options.nr)
> > +                     gtransport->server_options = &server_options;
> > +             result = transport_fetch_refs(gtransport, NULL);
> > +     } else if (negotiate_only) {
> >               struct oidset acked_commits = OIDSET_INIT;
> >               struct oidset_iter iter;
> >               const struct object_id *oid;
> > diff --git a/fetch-pack.c b/fetch-pack.c
> > index b709a61baf..36e3d1c5d0 100644
> > --- a/fetch-pack.c
> > +++ b/fetch-pack.c
> > @@ -1269,6 +1269,27 @@ static void write_command_and_capabilities(struct strbuf *req_buf,
> >       packet_buf_delim(req_buf);
> >  }
> >
> > +void send_object_info_request(int fd_out, struct object_info_args *args)
> > +{
> > +     struct strbuf req_buf = STRBUF_INIT;
> > +     int i;
>
> I don't think this would ever be practically exploit-able, since we'd
> run past the argument limit long before we hit INT_MAX, but this should
> be a size_t instead of an int to match the type of args->oid->nr.
>
> > +
> > +     write_command_and_capabilities(&req_buf, args->server_options, "object-info");
> > +
> > +     if (string_list_has_string(args->object_info_options, "size"))
> > +             packet_buf_write(&req_buf, "size");
> > +
> > +     for (i = 0; i < args->oids->nr; i++) {
> > +             packet_buf_write(&req_buf, "oid %s\n", oid_to_hex(&args->oids->oid[i]));
> > +     }
>
> Small nit, the braces around this for-loop are not required.
>
> >  static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
> >                             struct fetch_pack_args *args,
> >                             const struct ref *wants, struct oidset *common,
> > @@ -1604,6 +1625,10 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
> >       if (args->depth > 0 || args->deepen_since || args->deepen_not)
> >               args->deepen = 1;
> >
> > +     if (args->object_info) {
> > +             state = FETCH_SEND_REQUEST;
> > +     }
> > +
>
> Ditto here.
>
> >       while (state != FETCH_DONE) {
> >               switch (state) {
> >               case FETCH_CHECK_LOCAL:
> > @@ -1613,7 +1638,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
> >                       /* Filter 'ref' by 'sought' and those that aren't local */
> >                       mark_complete_and_common_ref(negotiator, args, &ref);
> >                       filter_refs(args, &ref, sought, nr_sought);
> > -                     if (everything_local(args, &ref))
> > +                     if (!args->object_info && everything_local(args, &ref))
> >                               state = FETCH_DONE;
> >                       else
> >                               state = FETCH_SEND_REQUEST;
> > @@ -1999,8 +2024,19 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
> >               }
> >               args->connectivity_checked = 1;
> >       }
> > -
> > -     update_shallow(args, sought, nr_sought, &si);
> > +
> > +     if (args->object_info) {
> > +             struct ref *ref_cpy_reader = ref_cpy;
> > +             unsigned long size = 0;
> > +             while (ref_cpy_reader) {
> > +                     oid_object_info(the_repository, &(ref_cpy_reader->old_oid), &size);
> > +                     printf("%s %li\n", oid_to_hex(&(ref_cpy_reader->old_oid)), size);
>
> Both expressions like "&(x)" can be written instead as "&x" without the
> outer parenthesis.
>
> Likewise, we do not use %li, that line should instead read:
>
>     printf("%s %"PRIuMAX"\n", oid_to_hex(&ref_cpy_reader->old_oid), (uintmax_t)size);
>
> Thanks,
> Taylor