For 'svn diff' especially, if we don't print the notifications, then we miss out on informing the user during one of the times when it could be particularly valuable to them. (They are waiting for diff output, which previously in svn used to come quickly.)
It would be ugly to print these notifications in the stdout stream. Diff output format rules do allow it to contain new informative lines outside the diff hunks, but this kind of notification would not be useful or nice for consumers of the diff. Print progress notifications to stderr? That is what some other command-line tools do. Some even have command-line flags to control where it is sent. One precedent we have is warnings, e.g. in "svn proplist nonexistent-target valid-target" a warning about 'nonexistent-target' goes to stderr while the primary output for 'valid-target' goes to stdout. I am not sure how I feel about printing them to stderr. I could be persuaded either way (print them to stderr or not at all). Anybody want to recommend what we should do for 'cat' and 'diff'? For the time being I am going to make 'svn' suppress hydrating notifications for 'cat' and 'diff'. We will at least get the benefit for the other subcommands. This is only a concern for command-line clients. GUIs have other ways to separate the progress notifications from the primary output. Therefore this is all a question of what to do in the client layer, the 'svn' executable; the library will continue to call the notification call-back if the client supplies one. - Julian
