[PATCH 2/5] add: allow operating on a sparse-only index

From: Derrick Stolee <redacted>

Disable command_requires_full_index for 'git add'. This does not require
any additional removals of ensure_full_index(). The main reason is that
'git add' discovers changes based on the pathspec and the worktree
itself. These are then inserted into the index directly, and calls to
index_name_pos() or index_file_exists() already call expand_to_path() at
the appropriate time to support a sparse-index.

Add a test to check that 'git add -A' and 'git add <file>' does not
expand the index at all, as long as <file> is not within a sparse
directory. This does not help the global 'git add .' case.

We can measure the improvement using p2000-sparse-operations.sh with
these results:

Test                                  HEAD~1           HEAD
------------------------------------------------------------------------------
2000.6: git add -A (full-index-v3)    0.35(0.30+0.05)  0.37(0.29+0.06) +5.7%
2000.7: git add -A (full-index-v4)    0.31(0.26+0.06)  0.33(0.27+0.06) +6.5%
2000.8: git add -A (sparse-index-v3)  0.57(0.53+0.07)  0.05(0.04+0.08) -91.2%
2000.9: git add -A (sparse-index-v4)  0.58(0.55+0.06)  0.05(0.05+0.06) -91.4%

While the 91% improvement seems impressive, it's important to recognize
that previously we had significant overhead for expanding the
sparse-index. Comparing to the full index case, 'git add -A' goes from
0.37s to 0.05s, which is "only" an 86% improvement.

Signed-off-by: Derrick Stolee <redacted>
---
 builtin/add.c                            |  3 +++
 t/t1092-sparse-checkout-compatibility.sh | 14 ++++++--------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/builtin/add.c b/builtin/add.c
index b773b5a4993..c76e6ddd359 100644
--- a/builtin/add.c
+++ b/builtin/add.c

@@ -528,6 +528,9 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	add_new_files = !take_worktree_changes && !refresh_only && !add_renormalize;
 	require_pathspec = !(take_worktree_changes || (0 < addremove_explicit));
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 
 	/*

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index a3c01d588d8..a11d9d7f35d 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh

@@ -340,13 +340,6 @@ test_expect_success 'status/add: outside sparse cone' '
 
 	test_sparse_match git status --porcelain=v2 &&
 
-	# This "git add folder1/a" fails with a warning
-	# in the sparse repos, differing from the full
-	# repo. This is intentional.
-	test_sparse_match test_must_fail git add folder1/a &&
-	test_sparse_match test_must_fail git add --refresh folder1/a &&
-	test_all_match git status --porcelain=v2 &&
-
 	test_all_match git add . &&
 	test_all_match git status --porcelain=v2 &&
 	test_all_match git commit -m folder1/new &&

@@ -635,7 +628,12 @@ test_expect_success 'sparse-index is not expanded' '
 	git -C sparse-index reset --hard &&
 	ensure_not_expanded checkout rename-out-to-out -- deep/deeper1 &&
 	git -C sparse-index reset --hard &&
-	ensure_not_expanded restore -s rename-out-to-out -- deep/deeper1
+	ensure_not_expanded restore -s rename-out-to-out -- deep/deeper1 &&
+
+	echo >>sparse-index/README.md &&
+	ensure_not_expanded add -A &&
+	echo >>sparse-index/extra.txt &&
+	ensure_not_expanded add extra.txt
 '
 
 # NEEDSWORK: a sparse-checkout behaves differently from a full checkout

-- 
gitgitgadget