[PATCH v3 15/15] config: handle NULL values when listing colors and expiry dates

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

From: Thomas Bachem <mail@thomasbachem.com>

Since 2d4ab5a885 (config: format colors quietly, 2026-02-23) and
9cb4a5e1ba (config: format expiry dates quietly, 2026-02-23),
"git config list --type=color" and "--type=expiry-date" pass every
value to color_parse_quietly() or parse_expiry_date(), which do not
handle NULL. So both segfault when any key in the configuration has
no value.

Skip such a key quietly, as both already do with a value that does
not parse, and as "--type=int" does with a key without a value.

Assisted-by: Claude Opus 5.5
Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
---
 builtin/config.c  |  4 ++--
 t/t1300-config.sh | 10 ++++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/builtin/config.c b/builtin/config.c
index 2554322317..f786c0b123 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -366,7 +366,7 @@ static int format_config_expiry_date(struct strbuf *buf,
 {
 	timestamp_t t;
 	if (quietly) {
-		if (parse_expiry_date(value_, &t))
+		if (!value_ || parse_expiry_date(value_, &t))
 			return -1;
 	} else if (git_config_expiry_date(&t, key_, value_) < 0) {
 		return -1;
@@ -384,7 +384,7 @@ static int format_config_color(struct strbuf *buf,
 	char v[COLOR_MAXLEN];
 
 	if (gently) {
-		if (color_parse_quietly(value_, v) < 0)
+		if (!value_ || color_parse_quietly(value_, v) < 0)
 			return -1;
 	} else if (git_config_color(v, key_, value_) < 0) {
 		return -1;
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index 8fb920b1ba..3322b0bf4f 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -2648,6 +2648,16 @@ test_expect_success 'list --type=color shows only canonicalizable color values'
 	test_must_be_empty err
 '
 
+test_expect_success 'list --type=color and --type=expiry-date skip keys without a value' '
+	git -c section.valueless config ${mode_prefix}list --type=color >actual 2>err &&
+	test_grep ! valueless actual &&
+	test_must_be_empty err &&
+
+	git -c section.valueless config ${mode_prefix}list --type=expiry-date >actual 2>err &&
+	test_grep ! valueless actual &&
+	test_must_be_empty err
+'
+
 test_expect_success '--type rejects unknown specifiers' '
 	test_must_fail git config --type=nonsense section.foo 2>error &&
 	test_grep "unrecognized --type argument" error
-- 
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