Zsh completion should also show single letter options

[kiryph]

When I try to list available options with tab completion after a single dash, the zsh completion returns:

$ dep -<TAB>
-- no matches found --

With two dashes I get

❯ dep --<TAB>
-- option --
--help            -- Display help for the given command. When no command is given display help for the list command
--no-ansi         -- Force (or disable --no-ansi) ANSI output
--no-interaction  -- Do not ask any interactive question
--quiet           -- Do not output any message
--raw             -- To output raw command list
--short           -- To skip describing commands' arguments
--verbose         -- Increase the verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug
--version         -- Display this application version

Compare to the zsh completion of man

$ man -<TAB>
-- option --
--help       -h  -- display help information
--path       -w  -- display file locations
--preformat  -F  -- format man page only (do not display)
--version    -v  -- display version information
-B               -- specify browser to use for HTML files
-C               -- specify configuration file
-D               -- display man page along with debugging information
-H               -- specify command to render HTML as text
...