This is based on ld/sparse-index-blame (merged with 'master' due to an
unrelated build issue).

Here are two relatively-simple patches that further the sparse index
integrations.

Did you know that 'fetch' and 'pull' read the index? I didn't, or this would
have been an integration much earlier in the cycle. They read the index to
look for the .gitmodules file in case there are submodules that need to be
fetched. Since looking for a file by name is already protected, we only need
to disable 'command_requires_full_index' and we are done.

The 'ls-files' builtin is useful when debugging the index, and some scripts
use it, too. We are not changing the default behavior which expands a sparse
index in order to show all of the cached blobs. Instead, we add a '--sparse'
option that allows us to see the sparse directory entries upon request.
Combined with --debug, we can see a lot of index details, such as:

$ git ls-files --debug --sparse
LICENSE
  ctime: 1634910503:287405820
  mtime: 1634910503:287405820
  dev: 16777220 ino: 119325319
  uid: 501  gid: 20
  size: 1098    flags: 200000
README.md
  ctime: 1634910503:288090279
  mtime: 1634910503:288090279
  dev: 16777220 ino: 119325320
  uid: 501  gid: 20
  size: 934 flags: 200000
bin/index.js
  ctime: 1634910767:828434033
  mtime: 1634910767:828434033
  dev: 16777220 ino: 119325520
  uid: 501  gid: 20
  size: 7292    flags: 200000
examples/
  ctime: 0:0
  mtime: 0:0
  dev: 0    ino: 0
  uid: 0    gid: 0
  size: 0   flags: 40004000
package.json
  ctime: 1634910503:288676330
  mtime: 1634910503:288676330
  dev: 16777220 ino: 119325321
  uid: 501  gid: 20
  size: 680 flags: 200000

(In this example, the 'examples/' directory is sparse.)

Thanks!

Updates in v2
=============

 * Rebased onto latest ld/sparse-index-blame without issue.
 * Updated the test to use diff-of-diffs instead of a sequence of greps.
 * Added patches that remove the use of 'test-tool read-cache --table' and
   its implementation.

Updates in v3
=============

 * Fixed typo in commit message.
 * Added comments around doing strange things in an ls-files test.
 * Fixed adjacent typo in a test comment.

Derrick Stolee (5):
  fetch/pull: use the sparse index
  ls-files: add --sparse option
  t1092: replace 'read-cache --table' with 'ls-files --sparse'
  t1091/t3705: remove 'test-tool read-cache --table'
  test-read-cache: remove --table, --expand options

 Documentation/git-ls-files.txt           |   4 +
 builtin/fetch.c                          |   2 +
 builtin/ls-files.c                       |  12 +-
 builtin/pull.c                           |   2 +
 t/helper/test-read-cache.c               |  64 ++---------
 t/t1091-sparse-checkout-builtin.sh       |  25 ++++-
 t/t1092-sparse-checkout-compatibility.sh | 137 ++++++++++++++++++++---
 t/t3705-add-sparse-checkout.sh           |   8 +-
 8 files changed, 172 insertions(+), 82 deletions(-)

base-commit: 3fffe69d24e4ecc95246766f5396303a953695ff

Submitted-As: https://lore.kernel.org/git/pull.1080.v3.git.1639149192.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1080.git.1637077083.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1080.v2.git.1638992395.gitgitgadget@gmail.com