Fix "git clone" for git:// protocol

In ba22785(Reduce the number of connects when fetching), we checked
the return value of git_connect() to see if the connection was
successful.

However, for the git:// protocol, there is no need to have another
process, so the return value was NULL.

Now, it makes sense to assume the rule that git_connect() will return
NULL if it fails (at the moment, it die()s if it fails), so return
a dummy child process.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Acked-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

connect.c

@@ -472,14 +472,18 @@ char *get_port(char *host)
 	return NULL;
 }
 
+static struct child_process no_fork;
+
 /*
- * This returns NULL if the transport protocol does not need fork(2), or a
- * struct child_process object if it does.  Once done, finish the connection
- * with finish_connect() with the value returned from this function
- * (it is safe to call finish_connect() with NULL to support the former
- * case).
+ * This returns a dummy child_process if the transport protocol does not
+ * need fork(2), or a struct child_process object if it does.  Once done,
+ * finish the connection with finish_connect() with the value returned from
+ * this function (it is safe to call finish_connect() with NULL to support
+ * the former case).
  *
- * If it returns, the connect is successful; it just dies on errors.
+ * If it returns, the connect is successful; it just dies on errors (this
+ * will hopefully be changed in a libification effort, to return NULL when
+ * the connection failed).
  */
 struct child_process *git_connect(int fd[2], const char *url_orig,
 				  const char *prog, int flags)
@@ -577,7 +581,7 @@ struct child_process *git_connect(int fd[2], const char *url_orig,
 		free(url);
 		if (free_path)
 			free(path);
-		return NULL;
+		return &no_fork;
 	}
 
 	conn = xcalloc(1, sizeof(*conn));
@@ -635,7 +639,7 @@ struct child_process *git_connect(int fd[2], const char *url_orig,
 int finish_connect(struct child_process *conn)
 {
 	int code;
-	if (!conn)
+	if (!conn || conn == &no_fork)
 		return 0;
 
 	code = finish_command(conn);