About This Patch:
-----------------
This patch has almost no reuse of previous patch's commits, because this
one redesigned the exclusion for various object types and reoganized the
commits. 

Commit (1): objects.c: introduce `exclude_level` enum

This commit introduce a new enum named `exclude_level` in object.c, it
contains three enumerated values: "ET_SELF", "ET_INCLUDE" and
"ET_REACHABLE". The commit only makes the definitions, without any
implementations.

Commit (2): Introduce function `match_packfile_uri_exclusions`

This one move the codes used for matching the URI protocols from
`want_found_object` to new function `match_packfile_uri_exclusions`. The
purpose is to improve code readability related to the feature and make
preparation for further extension about the matching and exclusion for
multiple object types.

Commit (3): Replace `show_data` with structure `show_info`

There is no feature related codes in this commit. This commit modified
the parameters in function `show_object` by replacing `show_data` with a
new structure `show_info`, this is another way of implementation about
the previous commit[1] in patch v5.

Commit (4): Introduce `uploadpack.excludeobject` configuration

This commit introduce a new and backward-compatible configuration named
`uploadpack.excludeobject`, the diff between old and new: 

	uploadpack.blobPackfileUri=<object-hash> <pack-hash> <uri>
        uploadpack.excludeobject=<object-hash> <level> <pack-hash> <uri>

The <level> is correspond to the exclusion scope of the given object,
and it's mentioned as `exclude_value` in object.c  by "Commit (1)".

Commit (6,8,10): Implementations for excluding commits, trees and tags

Commit (7,9,11): Tests for excluding excluding commits, trees and tags

Commit (12): Corresponding documentation modifications

bundle-uri And packfile-uri 
----------------------------

Ævar Arnfjörð Bjarmason post a new feature patchset[2] named "bundle-uri",
it supports to let client download the full or incremental bundles
directly without any negotiations with the server (full clone first and
in a MVP progress now). I'm sorry if I misleading the meanings and
please point it out.

In "packfile-uri", different with "bundle-uri", happens in the span of
packing objects during git-upload-pack on the server. This is an
experimental feature, originally designed as a CDN for large BLOB
objects, but it's not yet fully functional. I'm currently working on it
for making it support other types of objects.

I also noticed that some opinions about the two features are mentioned
in the patch[2], so I cc to Stolee in this patch, I hope I did not
disturb you.


[1] https://public-inbox.org/git/xmqqlf4oc4u1.fsf@gitster.g/
[2] https://lore.kernel.org/git/RFC-cover-00.13-0000000000-20210805T150534Z-avarab@gmail.com/ (local)

Teng Long (12):
  objects.c: introduce `exclude_level` enum
  Introduce function `match_packfile_uri_exclusions`
  Replace `show_data` with structure `show_info`
  Introduce `uploadpack.excludeobject` configuration
  t5702: test cases for `uploadpack.excludeobject`
  packfile-uri: support for excluding commits
  t5702: test cases for excluding commits
  packfile-uri: support for excluding trees
  t5702: test cases for excluding trees
  packfile-uri: support for excluding tags
  t5702: test cases for excluding tags
  packfile-uri.txt: support multiple object types

 Documentation/technical/packfile-uri.txt |  74 +-
 builtin/describe.c                       |   9 +-
 builtin/pack-objects.c                   | 236 +++++--
 builtin/rev-list.c                       |  11 +-
 bundle.c                                 |   5 +-
 list-objects.c                           |  74 +-
 list-objects.h                           |  11 +-
 object.c                                 |  21 +-
 object.h                                 |  16 +-
 pack-bitmap.c                            |  16 +-
 reachable.c                              |  11 +-
 revision.c                               |  47 +-
 revision.h                               |  12 +
 shallow.c                                |   4 +-
 t/t5702-protocol-v2.sh                   | 856 +++++++++++++++++++++--
 upload-pack.c                            |   7 +
 16 files changed, 1253 insertions(+), 157 deletions(-)

Range-diff against v5:
 1:  3a885678c9 =  1:  3a885678c9 objects.c: introduce `exclude_level` enum
 2:  36426b4d9f =  2:  36426b4d9f Introduce function `match_packfile_uri_exclusions`
 3:  dced036f89 =  3:  dced036f89 Replace `show_data` with structure `show_info`
 4:  b1d779b26a =  4:  b1d779b26a Introduce `uploadpack.excludeobject` configuration
 5:  f643db3c71 =  5:  f643db3c71 t5702: test cases for `uploadpack.excludeobject`
 6:  c29efeac21 =  6:  c29efeac21 packfile-uri: support for excluding commits
 7:  ca72efd22e =  7:  ca72efd22e t5702: test cases for excluding commits
 8:  c7a885ebec =  8:  c7a885ebec packfile-uri: support for excluding trees
 9:  5fc79a9a32 =  9:  5fc79a9a32 t5702: test cases for excluding trees
10:  16c41c40a2 = 10:  16c41c40a2 packfile-uri: support for excluding tags
11:  171ece533b = 11:  171ece533b t5702: test cases for excluding tags
12:  79fc2c23cf = 12:  79fc2c23cf packfile-uri.txt: support multiple object types
-- 
2.31.1.453.g945ddc3a74.dirty