Something I'd like information on is whether it is possible to upload a SPIFFS filesystem image to the ESP8266. In theory it might work: It can be uploaded over USB, and according to the logs the flash location changes, but that's about it. PlatformIO also seems to offer an Upload SPIFFS option in a platform that's set to an OTA port, but that could just be it not checking the upload type.
So, what I want to know is how I can configure (or otherwise make) a SPIFFS image OTA-uploadable. I have two main OTA methods: Option One is the default Arduino OTA library, and Option Two is a re-skin of the OTA method-whose-name-is-forgettable where I can upload a file on a webpage hosted by the ESP8266 and it will read the file and update its firmware.
I'm assuming that there's a configuration parameter for this somewhere, but I don't know where to start looking, and the documentation on these libraries has a few very basic examples that don't cover complex or advanced use cases.
(The web server--though essentially unrelated to this issue, it's a great example--is the most egregious of these; the code is complex and now templated too, so I can't make sense of it, and the "examples" consist largely of compressed javascript that doesn't show the user anything. Then you get to the interesting stuff like actually getting the real size of an uploading file, or want to know how uploading things actually works (or why it fails), or you want to serve a file piecemeal by assembling bits of text (in the same way that debug statements usually make use of multiple Serial.print() statements), and there's just nothing)
Updateobject from core