[PATCH 01/15] rebase -i: handle NULL value for rebase.missingCommitsCheck

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

From: Thomas Bachem <mail@thomasbachem.com>

A rebase.missingCommitsCheck without a value, as in

  [rebase]
  missingCommitsCheck

or "git -c rebase.missingCommitsCheck", makes "git rebase -i"
segfault as it writes the todo list: get_missing_commit_check_level()
passes the NULL value to strcasecmp().

The setting takes "ignore", "warn" or "error", not a bool. Read it
with repo_config_get_string_tmp(), which rejects a missing value with
config_error_nonbool(), as ba176db511 (config: handle NULL value when
parsing non-bools, 2023-12-07) did for other settings.

Assisted-by: Claude Fable 5.1
Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
---
 rebase-interactive.c          | 2 +-
 t/t3404-rebase-interactive.sh | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/rebase-interactive.c b/rebase-interactive.c
index 809f76a87b..4eb628ee8f 100644
--- a/rebase-interactive.c
+++ b/rebase-interactive.c
@@ -30,7 +30,7 @@ static enum missing_commit_check_level get_missing_commit_check_level(void)
 {
 	const char *value;
 
-	if (repo_config_get_value(the_repository, "rebase.missingcommitscheck", &value) ||
+	if (repo_config_get_string_tmp(the_repository, "rebase.missingcommitscheck", &value) ||
 			!strcasecmp("ignore", value))
 		return MISSING_COMMIT_CHECK_IGNORE;
 	if (!strcasecmp("warn", value))
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index ff11abb2f2..813ad2a83d 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -1562,6 +1562,13 @@ test_expect_success 'rebase -i respects rebase.missingCommitsCheck = error' '
 	test B = $(git cat-file commit HEAD^ | sed -ne \$p)
 '
 
+test_expect_success 'rebase -i rejects rebase.missingCommitsCheck without a value' '
+	rebase_setup_and_clean missing-commit &&
+	test_when_finished "test_might_fail git rebase --abort" &&
+	test_must_fail git -c rebase.missingCommitsCheck rebase -i --root 2>err &&
+	test_grep "missing value for .rebase.missingcommitscheck." err
+'
+
 test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = ignore' '
 	test_config rebase.missingCommitsCheck ignore &&
 	rebase_setup_and_clean missing-commit &&
-- 
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