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

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.

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(-)