Two checks around the upload, both cheap next to what they prevent.
Before: the snapshot is quick_checked before it leaves. It is the copy
every other device merges from, and a damaged one costs each of them a
download, a failed merge and a refusal to push.
After: the staged upload's size on the server is compared to the bytes
sent before it is rotated into place. A chunked upload is assembled
server-side, and an assembly that goes wrong is a file of plausible
size no device can open — caught here, on the device that caused it,
for one listing; otherwise on every other device, after the fact. A
mismatch, or a size the server will not confirm, discards the upload
and leaves the current copy and its generations untouched.
dtourolle
f100db89ca