[PATCH v2 03/10] sparse-checkout: add sanity-checks on initial sparsity state

["Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Elijah Newren <newren@gmail.com>

Most sparse-checkout subcommands (list, add, reapply, disable)
only make sense when already in a sparse state.  Add a quick check
that will error out early if this is not the case.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 builtin/sparse-checkout.c          | 12 ++++++++++++
 t/t1091-sparse-checkout-builtin.sh | 10 +++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index e252b82136e..e9f644ac362 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -56,6 +56,9 @@ static int sparse_checkout_list(int argc, const char **argv)
 	char *sparse_filename;
 	int res;
 
+	if (!core_apply_sparse_checkout)
+		die(_("this worktree is not sparse"));
+
 	argc = parse_options(argc, argv, NULL,
 			     builtin_sparse_checkout_list_options,
 			     builtin_sparse_checkout_list_usage, 0);
@@ -671,6 +674,9 @@ static int sparse_checkout_add(int argc, const char **argv, const char *prefix)
 		OPT_END(),
 	};
 
+	if (!core_apply_sparse_checkout)
+		die(_("no sparse-checkout to add to"));
+
 	repo_read_index(the_repository);
 
 	argc = parse_options(argc, argv, prefix,
@@ -719,6 +725,9 @@ static int sparse_checkout_reapply(int argc, const char **argv)
 		OPT_END(),
 	};
 
+	if (!core_apply_sparse_checkout)
+		die(_("must be in a sparse-checkout to reapply sparsity patterns"));
+
 	argc = parse_options(argc, argv, NULL,
 			     builtin_sparse_checkout_reapply_options,
 			     builtin_sparse_checkout_reapply_usage, 0);
@@ -740,6 +749,9 @@ static int sparse_checkout_disable(int argc, const char **argv)
 	struct pattern_list pl;
 	struct strbuf match_all = STRBUF_INIT;
 
+	if (!core_apply_sparse_checkout)
+		die(_("no active sparse-checkout to disable"));
+
 	argc = parse_options(argc, argv, NULL,
 			     builtin_sparse_checkout_disable_options,
 			     builtin_sparse_checkout_disable_usage, 0);
diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index 272ba1b566b..90a281bcf64 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -41,7 +41,15 @@ test_expect_success 'setup' '
 	)
 '
 
-test_expect_success 'git sparse-checkout list (empty)' '
+test_expect_success 'git sparse-checkout list (not sparse)' '
+	test_must_fail git -C repo sparse-checkout list >list 2>err &&
+	test_must_be_empty list &&
+	test_i18ngrep "this worktree is not sparse" err
+'
+
+test_expect_success 'git sparse-checkout list (not sparse)' '
+	git -C repo sparse-checkout set &&
+	rm repo/.git/info/sparse-checkout &&
 	git -C repo sparse-checkout list >list 2>err &&
 	test_must_be_empty list &&
 	test_i18ngrep "this worktree is not sparse (sparse-checkout file may not exist)" err
-- 
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