[PATCH v3 07/15] blame: handle NULL values for color.blame.* config

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

From: Thomas Bachem <mail@thomasbachem.com>

A color.blame.repeatedLines or color.blame.highlightRecent without a
value makes "git blame" segfault: git_blame_config() passes the NULL
value to strlen() or to parse_color_fields().

An invalid color.blame.repeatedLines gets a warning and is ignored.
Treat a missing value the same way.

An invalid color.blame.highlightRecent makes "git blame" die, so
reject a missing value there with config_error_nonbool(), as
git_blame_config() already does for blame.date and blame.coloring.

Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Assisted-by: Claude Fable 5.1
Assisted-by: Claude Opus 5.5
Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
---
 builtin/blame.c         |  7 +++++++
 t/t8012-blame-colors.sh | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/builtin/blame.c b/builtin/blame.c
index 1e753a0b60..55a3151942 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -783,12 +783,19 @@ static int git_blame_config(const char *var, const char *value,
 		return 0;
 	}
 	if (!strcmp(var, "color.blame.repeatedlines")) {
+		if (!value) {
+			warning(_("missing value for '%s'"),
+				"color.blame.repeatedLines");
+			return 0;
+		}
 		if (color_parse_mem(value, strlen(value), repeated_meta_color))
 			warning(_("invalid value for '%s': '%s'"),
 				"color.blame.repeatedLines", value);
 		return 0;
 	}
 	if (!strcmp(var, "color.blame.highlightrecent")) {
+		if (!value)
+			return config_error_nonbool(var);
 		parse_color_fields(value);
 		return 0;
 	}
diff --git a/t/t8012-blame-colors.sh b/t/t8012-blame-colors.sh
index d2653b3c31..2024047c85 100755
--- a/t/t8012-blame-colors.sh
+++ b/t/t8012-blame-colors.sh
@@ -69,4 +69,16 @@ test_expect_success 'blame color by age: new code is different' '
 	test_grep qfunc colored
 '
 
+test_expect_success 'color.blame.repeatedLines without a value only warns' '
+	git blame --color-lines hello.c >expect &&
+	git -c color.blame.repeatedLines blame --color-lines hello.c >actual 2>err &&
+	test_cmp expect actual &&
+	test_grep "missing value for .color.blame.repeatedLines." err
+'
+
+test_expect_success 'color.blame.highlightRecent needs a value' '
+	test_must_fail git -c color.blame.highlightRecent blame hello.c 2>err &&
+	test_grep "missing value for .color.blame.highlightrecent." err
+'
+
 test_done
-- 
gitgitgadget