cmdline/help: document -h [option]

And call the chapter 'help' instead of 'list options'

Fixes #504
Closes #522

SUMMARY.md

@@ -56,6 +56,7 @@
     * [Long options](cmdline/options/long.md)
     * [Arguments to options](cmdline/options/args.md)
     * [Negative options](cmdline/options/negative.md)
+  * [Help](cmdline/help.md)
   * [Options depend on version](cmdline/versions.md)
   * [URLs](cmdline/urls/README.md)
     * [Scheme](cmdline/urls/scheme.md)
@@ -72,7 +73,6 @@
     * [Connection reuse](cmdline/urls/connreuse.md)
     * [Parallel transfers](cmdline/urls/parallel.md)
     * [trurl](cmdline/urls/trurl.md)
-  * [List options](cmdline/listopts.md)
   * [Config file](cmdline/configfile.md)
   * [Variables](cmdline/variables.md)
   * [Passwords](cmdline/passwords.md)

cmdline/README.md

@@ -18,9 +18,9 @@ implementations in the most creative ways.
 
   * [Differences](differences.md)
   * [Command line options](options/)
+  * [Help](help.md)
   * [Options depend on version](versions.md)
   * [URLs](urls/)
-  * [List options](listopts.md)
   * [Config file](configfile.md)
   * [Variables](variables.md)
   * [Passwords](passwords.md)

cmdline/listopts.md → cmdline/help.md

@@ -1,19 +1,37 @@
-# List options
+# Help
 
-curl has more than two hundred and fifty command-line options and the number
+curl has more than two hundred and sixty command-line options and the number
 of options keep increasing over time. Chances are the number of options
 reaches or even surpasses three hundred in the coming years.
 
+## List options
+
 To find out which options you need to perform a certain action, you can get
 curl to list them. First, `curl --help` or simply `curl -h` get you a list of
 the most important and frequently used options. You can then provide an
 additional "category" to `-h` to get more options listed for that specific
 area. Use `curl -h category` to list all existing categories or `curl -h all`
 to list *all* available options.
 
+## Help with a specific option
+
+To get curl to display the documentation about a single specific command line
+option, add the option after `-h`. Use either the short name with a single
+dash (`-`) or the long version using two dashes (`--`).
+
+For example, learn what `-U` does by running
+
+    curl -h -U
+
+Or get `--insecure` explained like this:
+
+    curl -h --insecure
+
+## Full manual
+
 The `curl --manual` option outputs the entire man page for curl. That is a
 thorough and complete document on how each option works amassing several
 thousand lines of documentation. To wade through that is also a tedious work
 and we encourage use of a search function through those text masses. Some
-people might also appreciate the man page in its
-[web version](https://curl.se/docs/manpage.html).
+people might also appreciate the man page in its [web
+version](https://curl.se/docs/manpage.html).