timestamp auto-updating in files

timestamp.vim

" Add this to your vimrc file
" auto-update "Last update: " if present whenever saving file

autocmd! BufWritePre * :call s:timestamp()
" to update timestamp when saving if its in the first 5 lines of a file
function! s:timestamp()
    let pat = '\(Last update\s*:\s*\).*'
    let rep = '\1' . strftime("%Y-%m-%d %H:%M")
    call s:subst(1, 5, pat, rep)
endfunction
" subst taken from timestamp.vim
" {{{1 subst( start, end, pat, rep): substitute on range start - end.
function! s:subst(start, end, pat, rep)
    let lineno = a:start
    while lineno <= a:end
	let curline = getline(lineno)
	if match(curline, a:pat) != -1
	    let newline = substitute( curline, a:pat, a:rep, '' )
	    if( newline != curline )
		" Only substitute if we made a change
		"silent! undojoin
		keepjumps call setline(lineno, newline)
	    endif
	endif
	let lineno = lineno + 1
    endwhile
endfunction
" }}}1