Display warning when option doesn't have any effect?
In some cases, when rsync cannot apply an option, it is going to silently ignore it. This happens for example with -g when the user is not part of the file group and is not root.
I had this problem recently when I used rsync to backup a directory on a server. I later restored the dir but of course I didn't notice that groups hadn't been backed up, which in turns broke the server.
I had a similar issue with --chmod, which must be used with --perms or else it's also silently ignored, and there are probably other cases.
I think it would be more user-friendly to display a warning when options are going to be ignored. Something like this:
rsync: group ownership cannot be set on path/to/file due to a lack of permissions
rsync: --chmod option is going to be ignored since --perms is not enabled
So I'm wondering, would there be any interest in this feature? If I write a patch for it, is it likely to be accepted?