bug#34130: bug#6615: bug#34130: Specifying File Variables: mention why can't specify "current file"

[Robert Pluim]

>>>>> On Fri, 04 Oct 2019 16:11:17 +0800, 積丹尼 Dan Jacobson 
>>>>> <jidanni@jidanni.org> said:

    積丹尼> Whatever you are proposing is too complex.
    積丹尼> @CURRENT_FILE@ should just refer to the current file, no hacks needed.

You propose @CURRENT_FILE@, someone else will prefer $..$, someone
else again will want a different set of variables available. This is
why the 'eval' functionality exists, which you donʼt want to use,
hence the proposal to use the hook.

Robert