[FIX] Fixes issue with hirak/prestissimo

Trying to get options for `update` subcommand can result in long
waiting period an seemingly unresponsive bach completion when
composer plugin hirak/prestissimo is being used.
The latter will prefetch repositories whenever encountering the
subcommands `install`, `update` and the likes. When a project uses may
dependencies and repositories, this can take a while. An issue has also
been filed with prestissimo plugin (see hirak/prestissimo#225)
yet using the `help [command]` subcommand in favor to `[command] -h`
in order to retrieve all available options seems more reliable anyway.

composer-autocomplete

@@ -19,7 +19,7 @@ function _composer_scripts() {
     # Complete the arguments to some of the commands.
     #
     if [ "$subcmd" != "${COMP_WORDS[0]}" ] ; then
-        local opts=$("$cmd" "$subcmd" -h --no-ansi 2> /dev/null | tr -cs '[=-=][:alpha:]_' '[\n*]' | grep '^-')
+        local opts=$("$cmd" help "$subcmd" --no-ansi 2> /dev/null | tr -cs '[=-=][:alpha:]_' '[\n*]' | grep '^-')
         case "$subcmd" in
             "run-script")
                 # Complete scripts for composer "run-script" command.