After publishing an artifact to the repository. Ivy uploads an ivy.xml and generates related .md5 .sha1 files.
With a cleaned ivy cache the buildnumber task gives the wrong result when the ivy.xml in the repository is changed without changing the hash files.
This is ok, as there is at least a warning. But currently there is nothing. The ivy:buildnumber task runs without a message and returns the "possibly" wrong next revision.