This is useful because the variable definition, including the :safe:' declaration, is only loaded as the package is loaded. If the user sets the variable locally (e.g. inLocal Variables') and then visits that file in a new session before opening ebib for the first time, the safe predicate won't be recognised and the user is prompted for whether to use the new value. Using an autoload is the solution to this suggested in the elisp manual `(elisp) File Local Variables'.
This is an improvement on #296.
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