1. I type <leader>
2. Plugin pops up a sidebar with "gc - fugitive commit, gd - fugitive diff" etc
3. I can continue typing my command

" <Leader>x     List all mappings defined in normal / visual mode that
" {Visual}<Leader>x start with <Leader>x (if any are defined and there is no
"           dedicated <Leader>x mapping itself).
function! s:MakeMappingHelperMappings()
    for l:i in range(65,90) + range(97,122)
        let l:char = nr2char(l:i)
        let l:map = '<Leader>' . l:char
        for l:mode in ['n', 'x']
            if ! empty(mapcheck(l:map, l:mode)) && empty(maparg(l:map, l:mode))
                execute printf('%snoremap %s :<C-u>%smap %s<CR>', l:mode, l:map, l:mode, l:map)
            endif
        endfor
    endfor
endfunction
call s:MakeMappingHelperMappings()
delfunction s:MakeMappingHelperMappings