The humor in (1) and (2) was too hard to perceive, apparently. Let's try a more left-brained approach.
Regarding overwriting Autoexec.bat, it is obvious that I should have been backing it up. Not stating that is me showing respect to slashdotters. Maybe you forgot the forum we are commenting on here?
The more subtle issue is that the file only works with a single name, so there is a source code versioning problem right off the bat.
Versioning it as, say, Autoexec_20150804.bat, would be a solution, except my story predates long filenames.
Copying it to, say, dated folders of the form yyyymmdd would also work...unless the mistaken overwrite happened on the same day as a large number of earlier edits.
The reality is that it is easy to open and edit Autoexec.bat.
Easy to keep a single backup of it. And harder to keep it properly backed up.
My tongue-in-cheek "lesson learned" was to not waste time documenting Autoexec.bat -- because it didn't matter. It was my Autoexec.bat only. There was no payback to messing with it further. And backup of it made it more problematic.
Another lesson learned here is "beware of automated backup processes". They can be too good. Propagating (in this case a zip of all my .BAT files) a problem to multiple other places. So, offlining, or alternating backups is part of a better solution. etc.
The real point? That there are a lot of lessons to be learned from editing one simple file. I had tried to document everything, so that it would be useable later...and ended up with nothing despite my best efforts at the time.
So humbleness is a big part of doing something well.
Speaking of a lack of humbleness, 0 K, how do you figure I learned the wrong lesson on (3) above?