regenerate unconditionally unless its incremental (#6917)
regenerate unconditionally unless its incremental (#6917)

Merge pull request 6917
jekyll/jekyll,Strangehill/jekyll,x-way/jekyll,x-way/jekyll,getandpost/jekyll.github.io,chrisfinazzo/jekyll,Strangehill/jekyll,jekyll/jekyll,tillgrallert/jekyll,fulldecent/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,ryanshaw/jekyll,Strangehill/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,getandpost/jekyll.github.io,Strangehill/jekyll,tillgrallert/jekyll,getandpost/jekyll.github.io,Strangehill/jekyll,jekyll/jekyll,tillgrallert/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,chrisfinazzo/jekyll,ryanshaw/jekyll,x-way/jekyll,ryanshaw/jekyll,yhironaka/yhironaka.github.io,fulldecent/jekyll,fulldecent/jekyll,tillgrallert/jekyll,jaybe-jekyll/jekyll,jekyll/jekyll,jaybe-jekyll/jekyll,fulldecent/jekyll