Please provide a new command line paramter (-debugsvek) that works like the (-keepfiles) parameter but uses the file PlantUML source file basename, this will prevent the file from being overwritten when using the -keepfiles option.
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You can download last beta: https://dl.dropboxusercontent.com/u/13064071/plantuml.jar
We did:- removed this -keepfiles options (ie ignored it to not break eventually scripts that would use it)- added a -debugsvek option that will, as you suggest, create files using the basename of the source .puml file.
Tell us if it does not fit your needs.