[PATCH 2/3] sparse-checkout: clear patterns when switching modes

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

From: Derrick Stolee <dstolee@microsoft.com>

Previously, when a user runs 'git sparse-checkout init --cone', the
existing patterns would remain, even if the patterns were not in cone
mode. This causes confusion as to how the patterns should work when
later 'git sparse-checkout add' commands append to the pattern list.

In fact, the way these patterns were modified was not even a strict
appending of patterns, but mutating and reordering patterns because of
how the paths were interpreted and rewritten.

As a first step, we shall start overwriting the pattern set completely
when switching to cone mode, unless the existing patterns already match
cone mode patterns. The 'use_cone_patterns' member is set to false if
the patterns fail to parse using cone mode restrictions.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 builtin/sparse-checkout.c          | 13 +++++++++++--
 t/t1091-sparse-checkout-builtin.sh |  9 ++++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index b45fd97a98b..fe76c3eedda 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -348,8 +348,17 @@ static int sparse_checkout_init(int argc, const char **argv)
 
 	/* If we already have a sparse-checkout file, use it. */
 	if (res >= 0) {
-		free(sparse_filename);
-		return update_working_directory(NULL);
+		if (pl.use_cone_patterns || !init_opts.cone_mode) {
+			free(sparse_filename);
+			return update_working_directory(NULL);
+		}
+
+		/*
+		 * At this point, note that if res >= 0 but pl.use_cone_patterns
+		 * is false, then we want to override the patterns with the
+		 * initial set of cone mode patterns.
+		 */
+		clear_pattern_list(&pl);
 	}
 
 	if (get_oid("HEAD", &oid)) {
diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index a429d2cc671..af0acd32bd9 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -108,7 +108,14 @@ test_expect_success 'switching to cone mode with non-cone mode patterns' '
 	git -C bad-patterns sparse-checkout init &&
 	git -C bad-patterns sparse-checkout add dir &&
 	git -C bad-patterns config core.sparseCheckoutCone true &&
-	git -C bad-patterns sparse-checkout add dir
+	git -C bad-patterns sparse-checkout add dir &&
+
+	git -C bad-patterns sparse-checkout init --cone &&
+	cat >expect <<-\EOF &&
+	/*
+	!/*/
+	EOF
+	test_cmp expect bad-patterns/.git/info/sparse-checkout
 '
 
 test_expect_success 'interaction with clone --no-checkout (unborn index)' '
-- 
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