I’m trying to find the specification that Vim uses for the documentation files (which have the regular .txt extension).
I want to convert some documentation from HTML format to a doc format that Vim can read and use with the regular :h mydoc syntax, in addition to using the familiar C-] and C-o commands to jump to any tags within the doc file.
There is a link on the Vim homepage that points to the specification, but the link is dead, and unfortunately Archive.org does not have a snapshot of the website.
I should have looked more carefully. The help format is described in the help file itself: