Some months ago I was trying to wrap my head around some classical constructions in homological algebra. I spent quite a lot of time with this, and decided it was worth it to write it down. I did, it's almost 20 pages, and it's been sitting there in a file since then.
It starts pedagogically enough, reproving well-known results, and then it gets into "surely folklore" territory, i.e. not hard results about well-known objects that I have never seen in print (and I did search quite a bit for them). Then it goes on to prove an auxiliary result which is taken for granted in a recent paper (this was my motivation to do all of this).
It might be hidden in Cartan-Eilenberg (a quite hard to read book nowadays, in my humble opinion), it might not. At any rate, I don't know what to do with this file. Should I forget it? Be happy that I understood all of that, and keep it for personal consultation? Post it in my website? In arXiv? Submit it somewhere? I thought I could try to remove the certainly well-known stuff at the beginning, and only keep the "folklore" stuff; then it could be a less than 10 pages note.
The question is, then, how do I deal with "possibly well-known, possibly unwritten results about some well-known construction"?