When user tries to set both quiet and failonerror attributes to 'true' with 'delete' task Ant reports an error: "quiet and failonerror cannot both be set to true" While I may not know some important reason for this for a mere user it looks like unnecessary restriction. Failonerror, as the doc says "Controls whether an error (such as a failure to delete a file) stops the build or is merely reported to the screen." I believe that when used with quiet attribute set to 'true' Ant should report an error on failure or don't display anything on success. Simple and intuitive :) I have a pretty long build script which displays a LOT of standard messages and I'm implementing 'quiet' switch for it. With current Ant behavior I won't be able to silence output of 'delete' tasks.
The logs you are trying to "quiet" are not actually error logs right ? They are the logs about "Deleting: /path/myfile.txt" etc... right ? Today quiet is meant to quiet the error log. So just removing the restriction on setting both quiet and failonerror won't solve your issue. What you need is either change the semantic of the existing quiet which would break backward compatibility or just a new attribute.