[PATCH 0/5] Sparse Index: Integrate with 'git add'

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

This patch series re-submits the 'git add' integration with sparse-index.
The performance gains are the same as before.

It is based on ds/commit-and-checkout-with-sparse-index.

This series was delayed from its initial submission for a couple reasons.

The first was because it was colliding with some changes in
mt/add-rm-in-sparse-checkout, so now we are far enough along that that
branch is in our history and we can work forwards.

The other concern was about how 'git add ' should respond when a path
outside of the sparse-checkout cone exists. One recommendation (that I am
failing to find a link to the message, sorry) was to disallow adding files
that would become index entries with SKIP_WORKTREE on. However, as I worked
towards that goal I found that change would cause problems for a realistic
scenario: merge conflicts outside of the sparse-checkout cone.

The first patch of this series adds tests that create merge conflicts
outside of the sparse cone and then presents different ways a user could
resolve the situation. We want all of them to be feasible, and this
includes:

 1. Reverting the file to a known version in history.
 2. Adding the file with its contents on disk.
 3. Moving the file to a new location in the sparse directory.

Without maintaining the behavior of adding files outside of the
sparse-checkout cone, we risk confusing users who get into this state. The
only workaround they would have is to modify their sparse-checkout
definition which might lead to expanding much more data than they need to
resolve the conflicts.

For that reason, I stopped trying to limit 'git add' to be within the cone.
I'm open to suggestions here, but we need an approach that works for
out-of-cone conflicts.

The one place I did continue to update is 'git add --refresh ' to match the
behavior added by mt/add-rm-in-sparse-checkout which outputs an error
message. This happens even when the file exists in the working directory,
but that seems appropriate enough.

Thanks, -Stolee

Derrick Stolee (5):
  t1092: test merge conflicts outside cone
  add: allow operating on a sparse-only index
  pathspec: stop calling ensure_full_index
  t1092: 'git add --refresh' difference with sparse-index
  add: ignore outside the sparse-checkout in refresh()

 builtin/add.c                            | 13 ++++-
 pathspec.c                               |  2 -
 t/t1092-sparse-checkout-compatibility.sh | 71 ++++++++++++++++++++----
 3 files changed, 72 insertions(+), 14 deletions(-)


base-commit: 71e301501c88399711a1bf8515d1747e92cfbb9b
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-999%2Fderrickstolee%2Fsparse-index%2Fadd-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-999/derrickstolee/sparse-index/add-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/999
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