clone: die on config error in cmd_clone

The clone command does not check for error codes returned by
`git_config_set` functions. This may cause the user to end up
with an inconsistent repository without any indication with what
went wrong.

Fix this problem by dying with an error message when we are
unable to write the configuration files to disk.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -783,12 +783,12 @@ static void write_refspec_config(const char *src_ref_prefix,
 		/* Configure the remote */
 		if (value.len) {
 			strbuf_addf(&key, "remote.%s.fetch", option_origin);
-			git_config_set_multivar(key.buf, value.buf, "^$", 0);
+			git_config_set_multivar_or_die(key.buf, value.buf, "^$", 0);
 			strbuf_reset(&key);
 
 			if (option_mirror) {
 				strbuf_addf(&key, "remote.%s.mirror", option_origin);
-				git_config_set(key.buf, "true");
+				git_config_set_or_die(key.buf, "true");
 				strbuf_reset(&key);
 			}
 		}
@@ -946,14 +946,14 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 			src_ref_prefix = "refs/";
 		strbuf_addstr(&branch_top, src_ref_prefix);
 
-		git_config_set("core.bare", "true");
+		git_config_set_or_die("core.bare", "true");
 	} else {
 		strbuf_addf(&branch_top, "refs/remotes/%s/", option_origin);
 	}
 
 	strbuf_addf(&value, "+%s*:%s*", src_ref_prefix, branch_top.buf);
 	strbuf_addf(&key, "remote.%s.url", option_origin);
-	git_config_set(key.buf, repo);
+	git_config_set_or_die(key.buf, repo);
 	strbuf_reset(&key);
 
 	if (option_reference.nr)