Initialize help when using redis-cli help or redis-cli ? (#10382)

The following usage will output an empty newline:
```
> redis-cli help set
empty line
```

The reason is that in interactive mode, we have called
`cliInitHelp`, which initializes help.

When using `redis-cli help xxx` or `redis-cli help ? xxx`,
we can't match the command due to empty `helpEntries`,
so we output an empty newline.

In this commit, we will call `cliInitHelp` to init the help.
Note that in this case, we need to call `cliInitHelp` (COMMAND DOCS)
every time, which i think is acceptable.

So now the output will look like:
```
[redis]# src/redis-cli help get

  GET key
  summary: Get the value of a key
  since: 1.0.0
  group: string

[redis]#
```

Fixes #10378

This PR also fix a redis-cli crash when using `--ldb --eval`:
```
[root]# src/redis-cli --ldb --eval test.lua test 1
Lua debugging session started, please use:
quit    -- End the session.
restart -- Restart the script in debug mode again.
help    -- Show Lua script debugging commands.

* Stopped at 1, stop reason = step over
-> 1   local num = redis.call('GET', KEYS[1]);
redis-cli: redis-cli.c:718: cliCountCommands: Assertion
`commandTable->element[i]->type == 1' failed.
Aborted
```
Because in ldb mode, `COMMAND DOCS` or `COMMAND` will
return an array, only with one element, and the type
is `REDIS_REPLY_STATUS`, the result is `<error> Unknown
Redis Lua debugger command or wrong number of arguments`.

So if we are in the ldb mode, and init the Redis HELP, we
will get the wrong response and crash the redis-cli.
In ldb mode we don't initialize HELP, help is only initialized
after the lua debugging session ends.

It was broken in #10043

src/redis-cli.c

@@ -282,7 +282,7 @@ static void usage(int err);
 static void slaveMode(void);
 char *redisGitSHA1(void);
 char *redisGitDirty(void);
-static int cliConnect(int force);
+static int cliConnect(int flags);
 
 static char *getInfoField(char *info, char *field);
 static long getLongInfoField(char *info, char *field);
@@ -800,7 +800,12 @@ static void cliInitHelp(void) {
     redisReply *commandTable;
     dict *groups;
 
-    if (cliConnect(CC_QUIET) == REDIS_ERR) return;
+    if (cliConnect(CC_QUIET) == REDIS_ERR) {
+        /* Can not connect to the server, but we still want to provide
+         * help, generate it only from the old help.h data instead. */
+        cliOldInitHelp();
+        return;
+    }
     commandTable = redisCommand(context, "COMMAND DOCS");
     if (commandTable == NULL || commandTable->type == REDIS_REPLY_ERROR) {
         /* New COMMAND DOCS subcommand not supported - generate help from old help.h data instead. */
@@ -870,6 +875,12 @@ static void cliOutputHelp(int argc, char **argv) {
         group = argv[0]+1;
     }
 
+    if (helpEntries == NULL) {
+        /* Initialize the help using the results of the COMMAND command.
+         * In case we are using redis-cli help XXX, we need to init it. */
+        cliInitHelp();
+    }
+
     assert(argc > 0);
     for (i = 0; i < helpEntriesLen; i++) {
         entry = &helpEntries[i];
@@ -1713,12 +1724,6 @@ static int cliSendCommand(int argc, char **argv, long repeat) {
     size_t *argvlen;
     int j, output_raw;
 
-    if (!config.eval_ldb && /* In debugging mode, let's pass "help" to Redis. */
-        (!strcasecmp(command,"help") || !strcasecmp(command,"?"))) {
-        cliOutputHelp(--argc, ++argv);
-        return REDIS_OK;
-    }
-
     if (context == NULL) return REDIS_ERR;
 
     output_raw = 0;
@@ -2420,6 +2425,17 @@ static int confirmWithYes(char *msg, int ignore_force) {
 }
 
 static int issueCommandRepeat(int argc, char **argv, long repeat) {
+    /* In Lua debugging mode, we want to pass the "help" to Redis to get
+     * it's own HELP message, rather than handle it by the CLI, see ldbRepl.
+     *
+     * For the normal Redis HELP, we can process it without a connection. */
+    if (!config.eval_ldb &&
+        (!strcasecmp(argv[0],"help") || !strcasecmp(argv[0],"?")))
+    {
+        cliOutputHelp(--argc, ++argv);
+        return REDIS_OK;
+    }
+
     while (1) {
         if (config.cluster_reissue_command || context == NULL ||
             context->err == REDIS_ERR_IO || context->err == REDIS_ERR_EOF)
@@ -2439,6 +2455,8 @@ static int issueCommandRepeat(int argc, char **argv, long repeat) {
         }
         if (cliSendCommand(argc,argv,repeat) != REDIS_OK) {
             cliPrintContextError();
+            redisFree(context);
+            context = NULL;
             return REDIS_ERR;
         }
 
@@ -2576,8 +2594,13 @@ static void repl(void) {
     int argc;
     sds *argv;
 
+    /* There is no need to initialize redis HELP when we are in lua debugger mode.
+     * It has its own HELP and commands (COMMAND or COMMAND DOCS will fail and got nothing).
+     * We will initialize the redis HELP after the Lua debugging session ended.*/
+    if (!config.eval_ldb) {
         /* Initialize the help using the results of the COMMAND command. */
         cliInitHelp();
+    }
 
     config.interactive = 1;
     linenoiseSetMultiLine(1);
@@ -2679,6 +2702,7 @@ static void repl(void) {
                     printf("\n(Lua debugging session ended%s)\n\n",
                         config.eval_ldb_sync ? "" :
                         " -- dataset changes rolled back");
+                    cliInitHelp();
                 }
 
                 elapsed = mstime()-start_time;
@@ -9005,10 +9029,11 @@ int main(int argc, char **argv) {
     }
 
     /* Otherwise, we have some arguments to execute */
-    if (cliConnect(0) != REDIS_OK) exit(1);
     if (config.eval) {
+        if (cliConnect(0) != REDIS_OK) exit(1);
         return evalMode(argc,argv);
     } else {
+        cliConnect(CC_QUIET);
         return noninteractive(argc,argv);
     }
 }