Issues to address to get out of beta

[kenkendk]

@ts678

“FTP (Alternative)” breakage is a regression I have a hard time quantifying, but aftp is somewhat rare and “FTP” can often substitute for it. In addition I think the SIZE command getting in trouble requires the server to be non-compliant with the File Transfer Protocol standard in RFC 959 transfer parameters requirement:

I had a look at this. Unlike the other aftp issue, the SIZE issue arises from code in Duplicati.
Given that this is a non-compliant behavior, I think we can require the user to deal with it.

My idea is to add an option like --aftp-upload-delay=0s. This option is disabled (set to 0s) by default, giving the current behavior. If this option is set to a positive timespan, it will simply wait that amount of time instead of checking the remote size. This allows users to disable the failing SIZE check, and also get the upload delay if required, and adjustable to their network speed.

EDIT: Turns out there was already a --disable-upload-verify option meant to disable the SIZE check, but it was not doing anything. This means that the --aftp-upload-delay option only adds a wait delay, and users on non-compliant FTP servers need to set:

--disable-upload-verify=true
--aftp-upload-delay=5s

Any objections to that approach? @ts678 @BlueBlock

EDIT2: A proposed PR is here: Feature/aftp update by kenkendk · Pull Request #3956 · duplicati/duplicati · GitHub