In [1], we discovered that users working on different sparse-checkout
specification may download unnecessary blobs from each other's specification
in collaboration. In [2] Junio suggested that maybe we can restrict some git
command's filespec in sparse-checkout specification to elegantly solve this
problem above. In [3]: Newren and Derrick Stolee prefer to name the option
--scope={sparse, all}.

So this patch is attempt to do this thing on git diff:

v1:

 1. add --restrict option to git diff, which restrict diff filespec in
    sparse-checkout specification. [4]

v2.

 1. rename --restrict to --scope={sparse, all}, support --no-scope.
 2. add config: diff.scope={sparse,all}.

v3.

 1. with the help of newren's review, fix the wrong --scope behavior, its
    previous meaning was misrepresented as sparse patterns, and now it is
    fixed to match sparse specification. [5]
 2. remove wrong diff.scope config.
 3. apply --scope to git diff, git diff-index, git diff-tree.

v4.

 1. create a OPT_SPARSE_SCOPE macro for easier add --scope option to other
    git commands later.
 2. introduce --scope option to "git grep ".

Since I split --scope into a separate option, this option will not be
directly inherited by git commands such as git log, git format-patch, etc.
If necessary, we can add it to git log or other commands in a similar way
later.

Global scope config haven’t implement yet... Since we haven't decided on an
appropriate name for scope config. [6]

Note why I don't add --scope to "git grep --cached", because we can't use ""
with "--cached", whether we use --scope=sparse or not , the resulting set of
files it gets is the same.

[1]:
https://lore.kernel.org/git/CAOLTT8SHo66kGbvWr=+LQ9UVd1NHgqGGEYK2qq6==QgRCgLZqQ@mail.gmail.com/ (local)
[2]: https://lore.kernel.org/git/xmqqzgeqw0sy.fsf@gitster.g/ (local) [3]:
https://lore.kernel.org/git/07a25d48-e364-0d9b-6ffa-41a5984eb5db@github.com/ (local)
[4]:
https://lore.kernel.org/git/pull.1368.git.1664036052741.gitgitgadget@gmail.com/ (local)
[5]:
https://lore.kernel.org/git/CAOLTT8TceM-NpV2_hUCZj2Dx=W30f_9SHW8CcRH-pw32BRd-oA@mail.gmail.com/ (local)
[6]:
https://lore.kernel.org/git/CABPp-BGHMsMxP6e7p0HAZA=ugk+GY3XW6_EaTN=HzaLQYAzQYA@mail.gmail.com/ (local)

ZheNing Hu (2):
  [RFC] diff: introduce --scope option
  [RPC] grep: introduce --scope option

 Documentation/diff-options.txt   |  33 ++++
 Documentation/git-grep.txt       |  24 +++
 builtin/diff-index.c             |  24 ++-
 builtin/diff-tree.c              |  11 ++
 builtin/diff.c                   |  23 ++-
 builtin/grep.c                   |  10 +
 cache.h                          |   5 +
 diff-lib.c                       |  43 +++++
 diff.c                           |   2 +
 diff.h                           |   7 +
 dir.c                            |  52 ++++++
 dir.h                            |   4 +
 grep.h                           |   2 +
 parse-options.h                  |   7 +
 t/t1090-sparse-checkout-scope.sh | 303 +++++++++++++++++++++++++++++++
 tree-diff.c                      |   7 +
 16 files changed, 551 insertions(+), 6 deletions(-)


base-commit: 815c1e82021edbd99a2c423cf27f28863f28cef3
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1398%2Fadlternative%2Fzh%2Fdiff-scope-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1398/adlternative/zh/diff-scope-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1398

Contributor requested no range-diff. You can review it using these commands:
   git fetch https://github.com/gitgitgadget/git c000d916 1d1b6618
   git range-diff <options> c000d916..471a0691 083e0127..1d1b6618
-- 
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