docs: document missing arguments to commands

This is a followup to commit f410b9e538 fixing a few
more commands which takes arguments.

Closes #7382
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>

docs/cmdline-opts/parallel-max.d

@@ -1,4 +1,5 @@
 Long: parallel-max
+Arg: <num>
 Help: Maximum concurrency for parallel transfers
 Added: 7.66.0
 See-also: parallel

docs/cmdline-opts/quote.d

@@ -1,4 +1,5 @@
 Long: quote
+Arg: <command>
 Short: Q
 Help: Send command(s) to server before transfer
 Protocols: FTP SFTP

docs/cmdline-opts/request-target.d

@@ -1,4 +1,5 @@
 Long: request-target
+Arg: <path>
 Help: Specify the target for this request
 Protocols: HTTP
 Added: 7.55.0

src/tool_help.c

@@ -505,7 +505,7 @@ static const struct helptxt helptext[] = {
   {"    --parallel-immediate",
    "Do not wait for multiplexing (with --parallel)",
    CURLHELP_CONNECTION | CURLHELP_CURL},
-  {"    --parallel-max",
+  {"    --parallel-max <num>",
    "Maximum concurrency for parallel transfers",
    CURLHELP_CONNECTION | CURLHELP_CURL},
   {"    --pass <phrase>",
@@ -631,7 +631,7 @@ static const struct helptxt helptext[] = {
   {"    --pubkey <key>",
    "SSH Public key file name",
    CURLHELP_SFTP | CURLHELP_SCP | CURLHELP_AUTH},
-  {"-Q, --quote",
+  {"-Q, --quote <command>",
    "Send command(s) to server before transfer",
    CURLHELP_FTP | CURLHELP_SFTP},
   {"    --random-file <file>",
@@ -661,7 +661,7 @@ static const struct helptxt helptext[] = {
   {"-X, --request <command>",
    "Specify request command to use",
    CURLHELP_CONNECTION},
-  {"    --request-target",
+  {"    --request-target <path>",
    "Specify the target for this request",
    CURLHELP_HTTP},
   {"    --resolve <[+]host:port:addr[,addr]...>",