Let asdf help show plugin commands when available.

Also fix `asdf list all` to work as subcommand. Fixes #602

bin/asdf

@@ -26,7 +26,7 @@ find_asdf_cmd() {
   local asdf_cmd_dir
   asdf_cmd_dir="$(asdf_dir)/lib/commands"
   case "$1" in
-    ('exec' | 'current' | 'env' | 'global' | 'install' | 'latest' | 'list' | 'local' |\
+    ('exec' | 'current' | 'env' | 'global' | 'install' | 'latest' | 'local' |\
         'reshim' | 'uninstall' | 'update' | 'where' | 'which' |\
         'export-shell-version')
       echo "$asdf_cmd_dir/command-$1" 2

help.txt

@@ -22,7 +22,7 @@ MANAGE PACKAGES
   asdf local <name> <version>          Set the package local version
   asdf global <name> <version>         Set the package global version
   asdf list <name>                     List installed versions of a package
-  asdf list-all <name>                 List all versions of a package
+  asdf list all <name>                 List all versions of a package
 
 
 UTILS
@@ -32,7 +32,3 @@ UTILS
   asdf shim-versions <command>         List on which plugins and versions is command available
   asdf update                          Update asdf to the latest stable release
   asdf update --head                   Update asdf to the latest on the master branch
-
-
-"Late but latest"
--- Rajinikanth

lib/commands/command-help

@@ -1,9 +1,36 @@
 # -*- sh -*-
 
-help_command () {
+asdf_help() {
   echo "version: $(asdf_version)"
   echo ""
   cat "$(asdf_dir)/help.txt"
 }
 
+asdf_moto() {
+  cat <<EOF
+
+"Late but latest"
+-- Rajinikanth
+EOF
+}
+
+asdf_extension_cmds() {
+  local plugins_path ext_cmds
+  plugins_path="$(get_plugin_path)"
+  ext_cmds="$(ls -1 "$plugins_path"/*/bin/command* 2>/dev/null | sed "s#$plugins_path/#  asdf #;"'s#/bin/command##g;s#-# #g')"
+  if test -n "$ext_cmds"; then
+    echo "$ext_cmds" | cut -d' ' -f 4 | uniq | while read -r plugin; do
+      echo
+      echo "PLUGIN $plugin"
+      echo "$ext_cmds" | grep "  asdf $plugin"
+    done
+  fi
+}
+
+help_command() {
+  asdf_help
+  asdf_extension_cmds
+  asdf_moto
+}
+
 help_command "$@"