[BUG] Once start aof-use-rdb-preamble, redis does not use partial REPLICA after restarted

[kyangcmXF]

Describe the bug

I use redis6.0. However I found that redis slave does not always use partial REPLICA after restarted.

To reproduce

1. start aof-use-rdb-preamble in redis.conf
   aof-use-rdb-preamble yes
   2.restart redis6.0
   then the log is written that:

134:S 06 May 2022 20:05:19.957 * Connecting to MASTER 127.0.0.1:6379
134:S 06 May 2022 20:05:19.959 * MASTER <-> REPLICA sync started
134:S 06 May 2022 20:05:19.962 * Non blocking connect for SYNC fired the event.
134:S 06 May 2022 20:05:19.965 * Master replied to PING, replication can continue...
134:S 06 May 2022 20:05:19.968 * Partial resynchronization not possible (no cached master)
134:S 06 May 2022 20:05:25.224 * Full resync from master: 996dd0912cf1949fcd763d8db34897f6073c66da:191
134:S 06 May 2022 20:05:25.572 * MASTER <-> REPLICA sync: receiving streamed RDB from master with EOF to disk
134:S 06 May 2022 20:05:25.575 * MASTER <-> REPLICA sync: Flushing old data
134:S 06 May 2022 20:05:25.580 * MASTER <-> REPLICA sync: Loading DB in memory
134:S 06 May 2022 20:05:25.584 * Loading RDB produced by version 6.0.16
134:S 06 May 2022 20:05:25.586 * RDB age 0 seconds
134:S 06 May 2022 20:05:25.588 * RDB memory usage when created 1.49 Mb
134:S 06 May 2022 20:05:25.591 * MASTER <-> REPLICA sync: Finished with success

Expected behavior

I hope that slave redis will use partial REPLICA once restarted.

Additional information

I found why the aof file will not use partial replication. Because in aof.c does not save the redis slave info.
see below:
function: rewriteAppendOnlyFile()
the last para in rdbSaveRio is null. So why we pass null into it? Is there any meaningful thought?

`int rewriteAppendOnlyFile(char *filename) {
//do something

if (server.aof_use_rdb_preamble) {
    int error;
    if (rdbSaveRio(&aof,&error,RDBFLAGS_AOF_PREAMBLE,NULL) == C_ERR) {
        errno = error;
        goto werr;
    }
} else {
    if (rewriteAppendOnlyFileRio(&aof) == C_ERR) goto werr;
}

}`

[oranagra]

this topic is tracked in #9796