[PATCH v3 7/8] sparse-index: add SPARSE_INDEX_IGNORE_CONFIG flag

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 17, 2021, 13:23 UTC
Message-ID: <b0ece4b7dccf0cbe0477b3a6d238ea1362aed24d.1629206603.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1009.v3.git.1629206602.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

The convert_to_sparse() method checks for the GIT_TEST_SPARSE_INDEX environment variable or the "index.sparse" config setting before converting the index to a sparse one. This is for ease of use since all current consumers are preparing to compress the index before writing it to disk. If these settings are not enabled, then convert_to_sparse() silently returns without doing anything.

We will add a consumer in the next change that wants to use the sparse index as an in-memory data structure, regardless of whether the on-disk format should be sparse.

To that end, create the SPARSE_INDEX_IGNORE_CONFIG flag that will skip these config checks when enabled. All current consumers are modified to pass '0' in the new 'flags' parameter.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 read-cache.c   |  4 ++--
 sparse-index.c | 30 ++++++++++++++++--------------
 sparse-index.h |  3 ++-
 3 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index 9048ef9e905..f5d4385c408 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -3069,7 +3069,7 @@ static int do_write_locked_index(struct index_state *istate, struct lock_file *l
 	int ret;
 	int was_full = !istate->sparse_index;
 
-	ret = convert_to_sparse(istate);
+	ret = convert_to_sparse(istate, 0);
 
 	if (ret) {
 		warning(_("failed to convert to a sparse-index"));
@@ -3182,7 +3182,7 @@ static int write_shared_index(struct index_state *istate,
 	int ret, was_full = !istate->sparse_index;
 
 	move_cache_to_base_index(istate);
-	convert_to_sparse(istate);
+	convert_to_sparse(istate, 0);
 
 	trace2_region_enter_printf("index", "shared/do_write_index",
 				   the_repository, "%s", get_tempfile_path(*temp));
diff --git a/sparse-index.c b/sparse-index.c
index 2efc9fd4910..532fd11787e 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -124,7 +124,7 @@ static int index_has_unmerged_entries(struct index_state *istate)
 	return 0;
 }
 
-int convert_to_sparse(struct index_state *istate)
+int convert_to_sparse(struct index_state *istate, int flags)
 {
 	int test_env;
 
@@ -135,20 +135,22 @@ int convert_to_sparse(struct index_state *istate)
 	if (!istate->repo)
 		istate->repo = the_repository;
 
-	/*
-	 * The GIT_TEST_SPARSE_INDEX environment variable triggers the
-	 * index.sparse config variable to be on.
-	 */
-	test_env = git_env_bool("GIT_TEST_SPARSE_INDEX", -1);
-	if (test_env >= 0)
-		set_sparse_index_config(istate->repo, test_env);
+	if (!(flags & SPARSE_INDEX_IGNORE_CONFIG)) {
+		/*
+		 * The GIT_TEST_SPARSE_INDEX environment variable triggers the
+		 * index.sparse config variable to be on.
+		 */
+		test_env = git_env_bool("GIT_TEST_SPARSE_INDEX", -1);
+		if (test_env >= 0)
+			set_sparse_index_config(istate->repo, test_env);
 
-	/*
-	 * Only convert to sparse if index.sparse is set.
-	 */
-	prepare_repo_settings(istate->repo);
-	if (!istate->repo->settings.sparse_index)
-		return 0;
+		/*
+		 * Only convert to sparse if index.sparse is set.
+		 */
+		prepare_repo_settings(istate->repo);
+		if (!istate->repo->settings.sparse_index)
+			return 0;
+	}
 
 	if (init_sparse_checkout_patterns(istate) < 0)
 		return 0;
diff --git a/sparse-index.h b/sparse-index.h
index 1115a0d7dd9..475f4f0f8da 100644
--- a/sparse-index.h
+++ b/sparse-index.h
@@ -2,7 +2,8 @@
 #define SPARSE_INDEX_H__
 
 struct index_state;
-int convert_to_sparse(struct index_state *istate);
+#define SPARSE_INDEX_IGNORE_CONFIG (1 << 0)
+int convert_to_sparse(struct index_state *istate, int flags);
 
 /*
  * Some places in the codebase expect to search for a specific path.

-- 
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