Composer installer scripts create a .Packages folder
Since the last changes to the composer installer scripts a .Packages folder is created if for example TYPO3.Neos is installed. This happens because a folder is copied to folder '.' passed to Files::copyDirectoryRecursively() as target folder.
copyDirectoryRecursively() then prepends this to the source folder, resulting in the .Packages.
Question is if the copyDirectoryRecursively should append the / to prevent issues like this.