As far as I can tell: neither the Committer's Guide, nor the FreeBSD Documentation Project Primer for New Contributors, offers a plain warning. <https://docs.freebsd.org/en/articles/committers-guide/> <https://docs.freebsd.org/en/books/fdp-primer/book/> <https://reviews.freebsd.org/D37086#844064> exemplifies the error that may occur, with use of git-apply(1), if a trail exists: > … > warning: 2 lines add whitespace errors. <https://docs.freebsd.org/en/books/fdp-primer/book/#editor-config-nano-config> can be a clue only if the editor (the human) decides to read and interpret the content of the suggested ~/.nanorc file for nano(1).
I guess, this belongs somewhere under The FreeBSD Committers' Big List of Rules. <https://github.com/freebsd/freebsd-doc/blob/main/documentation/content/en/articles/committers-guide/_index.adoc#203-other-suggestions> currently has white space suggestions in the midst of the third paragraph. I'd split this paragraph; reorder and expand its content; make it more positive than negative … … and maybe include a link out/across to editor configuration, i.e. <https://github.com/freebsd/freebsd-doc/blob/main/documentation/content/en/books/fdp-primer/editor-config/_index.adoc>.
(In reply to Graham Perrin from comment #1) I'd add it to the FDP primer as well, under https://docs.freebsd.org/en/books/fdp-primer/writing-style/#writing-style-guidelines or elsewhere in that chapter.
(In reply to Pau Amma from comment #2) Agreed. Bug 267428 first.