Add missing variables

- add overlay_vars=, target_dir=, and tests= with short description

priv/shell-completion/zsh/_rebar

@@ -57,13 +57,16 @@ _rebar () {
         'suites[Common Test suites]::suite name:_path_files -W "(src test)" -g "*.erl(:r)"' \
         'verbose[Verbosity level]::verbosity level:(0 1 2 3)' \
         'appid[Application id]:' \
+        'overlay_vars[Overlay variables file]:' \
         'previous_release[Previous release path]:' \
         'nodeid[Node id]:' \
         'root_dir[Reltool config root directory]::directory:_files -/' \
         'skip_deps[Skip deps]::flag:(true false)' \
         'skip_apps[Application names to not process]::flag:(true false)' \
+        'target_dir[Target directory]:' \
         'template[Template name]:' \
         'template_dir[Template directory]::directory:_files -/' \
+        'tests[Run eunit tests whose name starts with given string]:' \
         && ret=0
       ;;
   esac