While using create is more correct, logs in Dokku are considered ephemeral, and thus shouldn't be considered subject to the more comprehensive log retention standards one might require out of a logging system.
By switching to copytruncate, we can ensure that logs mounted from within containers do not have that matched the old settings (closes#6633) and cases where the log file is written by a user other than the one specified in the old logrotate settings (closes#4000).
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