curl: help category cleanups

- add 'mqtt' as a category
- add more protocol categories to several options
- make --data worded better to also cover MQTT

Closes #22447

docs/cmdline-opts/abstract-unix-socket.md

@@ -6,7 +6,7 @@ Arg: <path>
 Help: Connect via abstract Unix domain socket
 Added: 7.53.0
 Protocols: HTTP
-Category: connection
+Category: connection http
 Multi: single
 See-also:
   - unix-socket

docs/cmdline-opts/basic.md

@@ -4,7 +4,7 @@ SPDX-License-Identifier: curl
 Long: basic
 Help: HTTP Basic Authentication
 Protocols: HTTP
-Category: auth
+Category: auth http
 Added: 7.10.6
 Multi: boolean
 See-also:

docs/cmdline-opts/compressed-ssh.md

@@ -5,7 +5,7 @@ Long: compressed-ssh
 Help: Enable SSH compression
 Protocols: SCP SFTP
 Added: 7.56.0
-Category: scp ssh
+Category: scp sftp ssh
 Multi: boolean
 See-also:
   - compressed

docs/cmdline-opts/data.md

@@ -4,16 +4,17 @@ SPDX-License-Identifier: curl
 Long: data
 Short: d
 Arg: <data>
-Help: HTTP POST data
+Help: Post data
 Protocols: HTTP MQTT
 Mutexed: form head upload-file
-Category: important http post upload
+Category: important http post upload mqtt
 Added: 4.0
 Multi: append
 See-also:
   - data-binary
   - data-urlencode
   - data-raw
+  - form
 Example:
   - -d "name=curl" $URL
   - -d "name=curl" -d "tool=cmdline" $URL
@@ -22,10 +23,14 @@ Example:
 
 # `--data`
 
-Send the specified data in a POST request to the HTTP server, in the same way
-that a browser does when a user has filled in an HTML form and presses the
-submit button. This option makes curl pass the data to the server using the
-content-type application/x-www-form-urlencoded. Compared to --form.
+Send the specified data to a server.
+
+For HTTP(S), this is done with the POST method in the same way that a browser
+does when a user has filled in an HTML form and presses the submit button.
+This option makes curl pass the data to the server using the content-type
+application/x-www-form-urlencoded.
+
+For MQTT, the data is sent as a PUBLISH.
 
 --data-raw is almost the same but does not have a special interpretation of
 the @ character. To post data purely binary, you should instead use the

docs/cmdline-opts/form-escape.md

@@ -5,7 +5,7 @@ Long: form-escape
 Help: Escape form fields using backslash
 Protocols: HTTP IMAP SMTP
 Added: 7.81.0
-Category: http upload post
+Category: http upload post imap smtp
 Multi: single
 See-also:
   - form

docs/cmdline-opts/key.md

@@ -5,7 +5,7 @@ Long: key
 Arg: <key>
 Protocols: TLS SCP SFTP
 Help: Private key filename
-Category: tls ssh
+Category: tls sftp scp ssh
 Added: 7.9.3
 Multi: single
 See-also:

docs/cmdline-opts/knownhosts.md

@@ -5,7 +5,7 @@ Long: knownhosts
 Arg: <file>
 Protocols: SCP SFTP
 Help: Specify knownhosts path
-Category: ssh
+Category: sftp scp ssh
 Added: 8.17.0
 Multi: single
 See-also:

docs/cmdline-opts/max-filesize.md

@@ -5,7 +5,7 @@ Long: max-filesize
 Arg: <bytes>
 Help: Maximum file size to download
 Protocols: FTP HTTP MQTT
-Category: connection
+Category: connection ftp http mqtt
 Added: 7.10.8
 Multi: single
 See-also:

docs/cmdline-opts/oauth2-bearer.md

@@ -5,7 +5,7 @@ Long: oauth2-bearer
 Help: OAuth 2 Bearer Token
 Arg: <token>
 Protocols: IMAP LDAP POP3 SMTP HTTP
-Category: auth imap pop3 smtp ldap
+Category: auth imap pop3 smtp ldap http
 Added: 7.33.0
 Multi: single
 See-also:

docs/cmdline-opts/pass.md

@@ -5,7 +5,7 @@ Long: pass
 Arg: <phrase>
 Help: Passphrase for the private key
 Protocols: TLS SCP SFTP
-Category: ssh tls auth
+Category: tls sftp scp ssh auth
 Added: 7.9.3
 Multi: single
 See-also:

docs/cmdline-opts/proxy-header.md

@@ -6,7 +6,7 @@ Arg: <header/@file>
 Help: Pass custom header(s) to proxy
 Protocols: HTTP
 Added: 7.37.0
-Category: proxy
+Category: proxy http
 Multi: append
 See-also:
   - proxy

docs/cmdline-opts/remote-header-name.md

@@ -5,7 +5,7 @@ Long: remote-header-name
 Short: J
 Protocols: HTTP
 Help: Use the header-provided filename
-Category: output
+Category: output http
 Added: 7.20.0
 Multi: boolean
 See-also:

docs/cmdline-opts/sasl-authzid.md

@@ -6,7 +6,7 @@ Arg: <identity>
 Help: Identity for SASL PLAIN authentication
 Protocols: LDAP IMAP POP3 SMTP
 Added: 7.66.0
-Category: auth
+Category: auth imap smtp pop3 ldap
 Multi: single
 See-also:
   - login-options

docs/cmdline-opts/sasl-ir.md

@@ -5,7 +5,7 @@ Long: sasl-ir
 Help: Initial response in SASL authentication
 Protocols: LDAP IMAP POP3 SMTP
 Added: 7.31.0
-Category: auth
+Category: auth imap pop3 ldap smtp
 Multi: boolean
 See-also:
   - sasl-authzid

docs/cmdline-opts/show-headers.md

@@ -5,7 +5,7 @@ Long: show-headers
 Short: i
 Help: Show response headers in output
 Protocols: HTTP FTP
-Category: important verbose output
+Category: important verbose output http ftp
 Added: 4.8
 Multi: boolean
 See-also:

docs/cmdline-opts/ssl-reqd.md

@@ -5,7 +5,7 @@ Long: ssl-reqd
 Help: Require SSL/TLS
 Protocols: FTP IMAP POP3 SMTP LDAP
 Added: 7.20.0
-Category: tls imap pop3 smtp ldap
+Category: tls imap pop3 smtp ldap ftp
 Multi: boolean
 See-also:
   - ssl

docs/cmdline-opts/ssl.md

@@ -5,7 +5,7 @@ Long: ssl
 Help: Try enabling TLS
 Protocols: FTP IMAP POP3 SMTP LDAP
 Added: 7.20.0
-Category: tls imap pop3 smtp ldap
+Category: tls imap pop3 smtp ldap ftp
 Multi: boolean
 See-also:
   - ssl-reqd

docs/cmdline-opts/unix-socket.md

@@ -6,7 +6,7 @@ Arg: <path>
 Help: Connect through this Unix domain socket
 Added: 7.40.0
 Protocols: HTTP
-Category: connection
+Category: connection http
 Multi: single
 See-also:
   - abstract-unix-socket

docs/cmdline-opts/upload-file.md

@@ -5,7 +5,7 @@ Long: upload-file
 Short: T
 Arg: <file>
 Help: Transfer local FILE to destination
-Category: important upload
+Category: important upload imap
 Added: 4.0
 Multi: per-URL
 See-also:

docs/cmdline-opts/upload-flags.md

@@ -5,7 +5,7 @@ Long: upload-flags
 Arg: <flags>
 Help: IMAP upload behavior
 Protocols: IMAP
-Category: curl output
+Category: curl output imap upload
 Added: 8.13.0
 Multi: single
 See-also: