I was synchronising some material, that isn't too large, that despite my slow connection speed, probably would not have taken long to sync.
However, I realised there was some additional stuff that I wanted to sync, so I added that material to the folder being synchronised as well. Obviously this means the sync will take longer, but it occurs to me that while I added more material sometime after syncing had begun on the first batch, SyncThing might well begin syncing the new material right away meaning that even if the first batch was nearly finished, it could be a long time before it is fully complete, because it's now sending all at the same time with the 2nd batch of material.
This makes me wonder, what the remote device to which I'm syncing (just one device) will see. Will they see nothing at all until the a given item is fully synchronised? Or will they see what is apparently a complete file but which is in reality missing data?
For instance, both batches of material are roughly 100-200MB video files in folders, I added the first folder and then around 40-50% in to sync, I added a second folder of similar materials. Is a folder treated as an 'item' as I'd conceive of it, and thus nothing is visible until the entire folder is sunc? Or Does syncthing synchronise the folder structure immediately and then gradually populate with folders located inside of that structure? If so, do individual files appear visible to the remote device's OS (Mac OSx for their end) only once they are a complete file, or are they accessible and visible even when only a few bytes have been synchronised?
I wonder because I hope that the remote device's users do not begin trying to use the material that's still synchronising if they have access to it on disk before it is fully sunc.