The grape command has options to install and list the currently installed "grapes". It needs an option to remove a "grape" as well.
The problem of the moment is pre-release snapshot software, e.g. groovyx.gpars:gpars:0.9-beta-1-SNAPSHOT. I keep updating this in my Maven cache but Grape never sees that it needs to re-grab from the Maven cache to the Grape cache. Currently I have to manually delete the files in teh Grape cache – which is silly.
Alternatively this could be seen as a bug in that Grape has no way of checking to see if it needs to do an update – it assumes the version number uniquely determines a jar, which is simply not true for SNAPSHOTs.