Release CHANGES IN bookdown VERSION 0.6 · rstudio/bookdown

NEW FEATURES

Added an argument config_file to render_book() so that one can specify a custom config file; the default config file is still _bookdown.yml (thanks, @stephlocke, #465).
Added a global option bookdown.preview.cutoff (defaults to 30) for the preview mode render_book(preview = TRUE): when the number of lines of a chapter is smaller or equal to this number, the full chapter is included in the preview; otherwise, only the section titles are extracted from the chapter for preview.

Various compatibility issues with Pandoc 2.0 (thanks, @maxheld83 #479, @jerrythomas #481, @Hantabaru #483, @dataopt #504, and #478).
split_by = 'section' does not work completely correctly for the HTML output formats like gitbook (thanks, @dataopt, #502).