I mean programmer documentation, how to build this thing, why was this choice made, what ideas were attempted and abandoned and why, what gotchas, what shortcut

I mean programmer documentation, how to build this thing, why was this choice made, what ideas were attempted and abandoned and why, what gotchas, what shortcuts were taken/tech debt incured. A lot of this should be in commit messages and/or "tickets" refed in commit messages. Rest goes into README, code comments. User docs are completely outside my realm as a software developer. My point (and strongly held belief) is NO, when you do testing and documentation is not really project dependent. All projects need to do it from the start. Some, flight control software, need more rigorous process. Everything needs to be viewed through ROI. My contention is too many devs underestimate the return of "doing it right" from the start. and overestimate the effort and effectiveness of doing it later/at the end.