[PATCH 8/8] sparse-checkout: integrate with sparse index

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: May 16, 2022, 18:11 UTC
Message-ID: <b8a349c6deeb4b970075629d0c292b2ae9f7d0d3.1652724693.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1208.git.1652724693.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

When modifying the sparse-checkout definition, the sparse-checkout builtin calls update_sparsity() to modify the SKIP_WORKTREE bits of all cache entries in the index. Before, we needed the index to be fully expanded in order to ensure we had the full list of files necessary that match the new patterns.

Insert a call to reset_sparse_directories() that expands sparse directories that are within the new pattern list, but only far enough that every necessary file path now exists as a cache entry. The remaining logic within update_sparsity() will modify the SKIP_WORKTREE bits appropriately.

This allows us to disable command_requires_full_index within the sparse-checkout builtin. Add tests that demonstrate that we are not expanding to a full index unnecessarily.

We can see the improved performance in the p2000 test script:

Test HEAD~1 HEAD ------------------------------------------------------------------------ 2000.24: git ... (sparse-v3) 2.14(1.55+0.58) 1.57(1.03+0.53) -26.6% 2000.25: git ... (sparse-v4) 2.20(1.62+0.57) 1.58(0.98+0.59) -28.2%

These reductions of 26-28% are small compared to most examples, but the time is dominated by writing a new copy of the base repository to the worktree and then deleting it again. The fact that the previous index expansion was such a large portion of the time is telling how important it is to complete this sparse index integration.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 builtin/sparse-checkout.c                |  3 +++
 t/t1092-sparse-checkout-compatibility.sh | 25 ++++++++++++++++++++++++
 unpack-trees.c                           |  4 ++++
 3 files changed, 32 insertions(+)

diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index cbff6ad00b0..0157b292b36 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -937,6 +937,9 @@ int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config, NULL);
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	if (argc > 0) {
 		if (!strcmp(argv[0], "list"))
 			return sparse_checkout_list(argc, argv);
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 93bcfd20bbc..614357fc48c 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -1552,6 +1552,31 @@ test_expect_success 'ls-files' '
 	ensure_not_expanded ls-files --sparse
 '
 
+test_expect_success 'sparse index is not expanded: sparse-checkout' '
+	init_repos &&
+
+	ensure_not_expanded sparse-checkout set deep/deeper2 &&
+	ensure_not_expanded sparse-checkout set deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set deep &&
+	ensure_not_expanded sparse-checkout add folder1 &&
+	ensure_not_expanded sparse-checkout set deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set folder2 &&
+
+	# Demonstrate that the checks that "folder1/a" is a file
+	# do not cause a sparse-index expansion (since it is in the
+	# sparse-checkout cone).
+	echo >>sparse-index/folder2/a &&
+	git -C sparse-index add folder2/a &&
+
+	ensure_not_expanded sparse-checkout add folder1 &&
+
+	# Skip checks here, since deep/deeper1 is inside a sparse directory
+	# that must be expanded to check whether `deep/deeper1` is a file
+	# or not.
+	ensure_not_expanded sparse-checkout set --skip-checks deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set
+'
+
 # NEEDSWORK: a sparse-checkout behaves differently from a full checkout
 # in this scenario, but it shouldn't.
 test_expect_success 'reset mixed and checkout orphan' '
diff --git a/unpack-trees.c b/unpack-trees.c
index 7f528d35cc2..9745e0dfc34 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -18,6 +18,7 @@
 #include "promisor-remote.h"
 #include "entry.h"
 #include "parallel-checkout.h"
+#include "sparse-index.h"
 
 /*
  * Error messages expected by scripts out of plumbing commands such as
@@ -2018,6 +2019,9 @@ enum update_sparsity_result update_sparsity(struct unpack_trees_options *o)
 			goto skip_sparse_checkout;
 	}
 
+	/* Expand sparse directories as needed */
+	expand_to_pattern_list(o->src_index, o->pl);
+
 	/* Set NEW_SKIP_WORKTREE on existing entries. */
 	mark_all_ce_unused(o->src_index);
 	mark_new_skip_worktree(o->pl, o->src_index, 0,

-- 
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