[PATCH v2 12/15] scalar: handle NULL value for scalar.repo

["Thomas Bachem via GitGitGadget" <gitgitgadget@gmail.com>]

From: Thomas Bachem <mail@thomasbachem.com>

A scalar.repo without a value makes "scalar reconfigure --all"
segfault: get_scalar_repos() passes the NULL value to
string_list_append(), which copies it with xstrdup().

Reject a missing value with config_error_nonbool(). This cannot break
a working setup, as "scalar register" always writes scalar.repo with
a path.

Assisted-by: Claude Opus 5.5
Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
---
 scalar.c          | 5 ++++-
 t/t9210-scalar.sh | 5 +++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/scalar.c b/scalar.c
index a80d8ee3ff..4fe4b2a647 100644
--- a/scalar.c
+++ b/scalar.c
@@ -652,8 +652,11 @@ static int get_scalar_repos(const char *key, const char *value,
 {
 	struct string_list *list = data;
 
-	if (!strcmp(key, "scalar.repo"))
+	if (!strcmp(key, "scalar.repo")) {
+		if (!value)
+			return config_error_nonbool(key);
 		string_list_append(list, value);
+	}
 
 	return 0;
 }
diff --git a/t/t9210-scalar.sh b/t/t9210-scalar.sh
index c8463d0ac4..137765d3b8 100755
--- a/t/t9210-scalar.sh
+++ b/t/t9210-scalar.sh
@@ -288,6 +288,11 @@ test_expect_success '`reconfigure -a` removes stale config entries' '
 	test_cmp expect scalar.repos
 '
 
+test_expect_success '`reconfigure -a` rejects scalar.repo without a value' '
+	test_must_fail scalar -c scalar.repo reconfigure -a 2>err &&
+	test_grep "missing value for .scalar.repo." err
+'
+
 test_expect_success 'scalar delete without enlistment shows a usage' '
 	test_expect_code 129 scalar delete
 '
-- 
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