fsck: handle NULL value when parsing message config

When parsing fsck.*, receive.fsck.*, or fetch.fsck.*, we don't check for
an implicit bool. So any of:

  [fsck]
  badTree
  [receive "fsck"]
  badTree
  [fetch "fsck"]
  badTree

will cause us to segfault. We can fix it with config_error_nonbool() in
the usual way, but we have to make a few more changes to get good error
messages. The problem is that all three spots do:

  if (skip_prefix(var, "fsck.", &var))

to match and parse the actual message id. But that means that "var" now
just says "badTree" instead of "receive.fsck.badTree", making the
resulting message confusing. We can fix that by storing the parsed
message id in its own separate variable.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/fsck.c b/fsck.c
index 6a0bbc5087..b624083a13 100644
--- a/fsck.c
+++ b/fsck.c
@@ -1403,6 +1403,8 @@ int git_fsck_config(const char *var, const char *value,
 		    const struct config_context *ctx, void *cb)
 {
 	struct fsck_options *options = cb;
+	const char *msg_id;
+
 	if (strcmp(var, "fsck.skiplist") == 0) {
 		const char *path;
 		struct strbuf sb = STRBUF_INIT;
@@ -1416,8 +1418,10 @@ int git_fsck_config(const char *var, const char *value,
 		return 0;
 	}
 
-	if (skip_prefix(var, "fsck.", &var)) {
-		fsck_set_msg_type(options, var, value);
+	if (skip_prefix(var, "fsck.", &msg_id)) {
+		if (!value)
+			return config_error_nonbool(var);
+		fsck_set_msg_type(options, msg_id, value);
 		return 0;
 	}