runtime ftplugin/text.vim
if !exists('b:markdown_autohtml')
let b:markdown_autohtml = 0
endif
function! s:autohtml() abort
if get(b:, 'markdown_autohtml', 0)
silent !md2html -o "%:p.html" "%:p"
endif
endfunction
augroup Markdown
autocmd!
autocmd BufWritePost <buffer> call s:autohtml()
augroup END