The deleted.files file in a plugin or template directory lists files or directories that should be deleted on update of the plugin by the Extension Manager.

Here's an example how such a file should look like.

lib/plugins/example/deleted.files

# This is a list of files that were present in previous plugin releases
# but were removed later. An up to date plugin should not have any of
# the files installed
youroldfile.php
folder/file.txt

Note: paths are relative to plugin or template folder that contains this file.

• Unused files on installation