Collapse help into expandable command topics

plugins/plugin/commands

@@ -4,7 +4,9 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 
 case "$1" in
   help | plugin:help)
-    cat<<EOF
+    help_content_func () {
+      declare desc="return help_content string"
+      cat<<help_content
     plugin, Print active plugins
     plugin:install [--core|git-url [--committish tag|branch|commit|--name custom-plugin-name]], Optionally download git-url (with custom tag/committish) & run install trigger for active plugins (or only core ones)
     plugin:install-dependencies [--core], Run install-dependencies trigger for active plugins (or only core ones)
@@ -12,7 +14,19 @@ case "$1" in
     plugin:enable <name>, Enable a previously disabled plugin
     plugin:disable <name>, Disable an installed plugin (third-party only)
     plugin:uninstall <name>, Uninstall a plugin (third-party only)
-EOF
+help_content
+    }
+
+    if [[ $1 = "plugin:help" ]] ; then
+        echo -e 'Usage: dokku plugin[:COMMAND]'
+        echo ''
+        echo 'View installed plugins and manage community plugins.'
+        echo ''
+        echo 'Additional commands:'
+        help_content_func | sort | column -c2 -t -s,
+    else
+        help_content_func
+    fi
     ;;
 
   *)