credential-cache: use child_process.args

As child_process structure has an embedded strvec args for
formulating the command line, let's use it instead of using
an out-of-line argv[] whose length needs to be maintained
correctly.

Also, when spawning a git subcommand, omit it from the command list
and instead use the .git_cmd bit in the child_process structure.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

credential-cache.c

@@ -39,13 +39,13 @@ static int send_request(const char *socket, const struct strbuf *out)
 static void spawn_daemon(const char *socket)
 {
 	struct child_process daemon = CHILD_PROCESS_INIT;
-	const char *argv[] = { NULL, NULL, NULL };
 	char buf[128];
 	int r;
 
-	argv[0] = "git-credential-cache--daemon";
+	strvec_pushl(&daemon.args,
-	argv[1] = socket;
+		     "credential-cache--daemon", socket,
-	daemon.argv = argv;
+		     NULL);
+	daemon.git_cmd = 1;
 	daemon.no_stdin = 1;
 	daemon.out = -1;