See https://forum.vyos.net/showthread.php?tid=26219

I tried to use this options:
scp://<user>:<passwd>@[IPv6-address]/<dir>
and also:
scp://<user>:<passwd>@"hostname"/<dir>, where "hostname" was in /etc/hostname file and I was able to ping6 it.
But with both configurations it failed to send config.

And proposed solution

We found the solution to this:
Add -g parameter to SCP commands in file /etc/commit/post-hooks.d/02vyatta-commit-push.pl row 89 and 103. After this curl is able to correctly parse the url.
for example in version 1.1.8 it looks like this: $cmd = "curl -g -s -S -T $tmp_push_file $uri/$save_file"; (it is twice in script)