This warning is very helpful but also frustrating... is there any way to find out which two .Rmds are missing first-level headings? (For the record, I did not write 72 chapters, this is a class project.)
Warning message: In split_chapters(output, gitbook_page, number_sections, split_by, : You have 72 Rmd input file(s) but only 70 first-level heading(s). Did you forget first-level headings in certain Rmd files?
Update: this was a false alarm... I changed two .Rmds to child documents while the book was rendering, creating a difference in count between
_bookdown.yml at the time rendering began, and the file count when render got to that point. Still, it would be helpful to know the answer for future reference.