Thank you for the contribution! This is great and the change looks good, would you mind adding a couple tests cases to tests/integration/targets/synchronize/tasks/main.yml?

Thank you!

I've looked at the code for the tests, but have a hard time figuring out how to make this work. All the current tests in tests/integration/targets/synchronize/tasks/main.yml run rsync with both src and dest on a local machine. Hence the r in rsync is never used. The bug described here only occurs when either src or dest is a remote path in the form user@server:/path/to/data. I've tried to simulate a remote path on the local machine with:

1. {{ lookup('env', 'USER') }}@localhost:{{ output_dir }}/foo.txt
2. {{ ansible_user }}@localhost:{{ output_dir }}/foo.txt
3. localhost:{{ output_dir }}/foo.txt

The first option fails because apparently ${USER} is undefined in the test environment as reported by ansible-test env
The second option also does work as {{ ansible_user }} does not exist in the test environment either.
Leaving the user out and only using localhost: will fail if the test environment does not have SSH login with public-private key pairs configured resulting in a password prompt. I can type that password on my laptop, but this won't fly in an automated CI environment...

!rebuild

/rebuild

Closing and reopening to rekick CI since the last time this one ran was on the old CI system

This is great, thanks! Approved and merging.