Implement auto-resume

[colemar]

If the remote host closes the connection axel stops. When given the same arguments again, axel resumes the download, provided that the web server supports it.
This happens today about every 3 minutes downloading from https://str-28.filestore.app/.
It would be great to have an option telling axel to resume the download by itself.

Axel 2.17.11 (linux-gnu)

[colemar]

Yes, there is a simple workaround:
while true; do axel ... ; done
But this is not ideal since it does not stop when the download is completed.

This seems to work though:
until axel ... ; do echo ---RESUME---; done