### Please describe the problem.
I'm trying to set up a gcrypt remote using the rsync backend because it can do incremental pushes. I know I won't be able to put annexed files on this remote, but even with `annex-ignore` set, the error arises.

### What steps will reproduce the problem?
[[!format sh """
% git remote add cryptremote gcrypt::rsync://host:repo
% git annex sync cryptremote

"""]]

### What version of git-annex are you using? On what operating system?
6.20181011-g426f0f3f4 on Arch Linux

### Please provide any additional information below.

[[!format sh """
git-annex: bad url rsync://host:repo
CallStack (from HasCallStack):
  error, called at ./Git/Construct.hs:101:15 in main:Git.Construct

"""]]

-- Lykos
