Re: [PATCH v4 0/8] cat-file: add --batch-command remote-object-info command

From: ZheNing Hu <adlternative@gmail.com>
Date: Jul 31, 2022, 15:02 UTC
Message-ID: <CAOLTT8Q-241cExFcbXSUfj42GontKH0uQpX1Voekf4RJ95hAVw@mail.gmail.com>
In-Reply-To: <20220502170904.2770649-1-calvinwan@google.com>

Hi, Calvin Wan,

Calvin Wan <calvinwan@google.com> 于2022年5月3日周二 08:14写道：

Show 21 quoted lines

>
> 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.
>
> Add `--object-info` option to `cat-file --batch-command`. This option
> allows the client to 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, the entire object is fetched and the
> relevant object info is returned.
>
> Summary of changes ==================
>
> Patches 1, 2, 3, and 7 are small changes that setup the main
> implementation. Patch 4 sets up object-info to be backwards compatible
> for future patch series that adds additional attributes.  Patch 5 adds
> internal trasnport functions to send and receive object-info command
> request packets. Patch 6 adds the fallback if object-info is not
> supported or fails.  Patch 8 adds the cat-file implementation.
>

I have to say I am very curious about this feature. Since the current git partial-clone interface supports only a few filters:

blob:limit blob:none sparse:oid tree:0

Though these filters reduce the number of objects downloaded each time, sometimes I just need *only* one blob object, git partial-clone will still download some additional commits and tree objects from the remote.

This patch can get the remote-object-info by git cat-file, so can we go further to get the remote-object-content of the object?

Something like:

$ git cat-file --batch-command remote-object-content origin <oid>

Show 37 quoted lines

> Changes since V3 ================
>
>  * Object-info is now implemented in cat-file --batch-command rather
>    than fetch (new base commit)
>  * Removed config option to advertise object-info
>  * Added forwards and backwards compability for object-info
>  * Split up some patches to better describe and visualize changes
>
> Signed-off-by: Calvin Wan <calvinwan@google.com>
> Helped-by: Jonathan Tan <jonathantanmy@google.com>
>
> Calvin Wan (8):
>   fetch-pack: refactor packet writing
>   fetch-pack: move fetch default settings
>   object-store: add function to free object_info contents
>   object-info: send attribute packet regardless of object ids
>   transport: add client side capability to request object-info
>   transport: add object-info fallback to fetch
>   cat-file: move parse_cmd and DEFAULT_FORMAT up
>   cat-file: add --batch-command remote-object-info command
>
>  Documentation/git-cat-file.txt |  16 +-
>  builtin/cat-file.c             | 225 ++++++++++++++++-----
>  fetch-pack.c                   |  61 ++++--
>  fetch-pack.h                   |  10 +
>  object-file.c                  |  16 ++
>  object-store.h                 |   3 +
>  protocol-caps.c                |  14 +-
>  t/t1006-cat-file.sh            | 347 +++++++++++++++++++++++++++++++++
>  transport-helper.c             |   7 +-
>  transport.c                    |  97 ++++++++-
>  transport.h                    |  11 ++
>  11 files changed, 728 insertions(+), 79 deletions(-)
>
> --
> 2.36.0.rc2.10170.gb555eefa6f
>

Thanks!

ZheNing Hu