* lisp/vc/ediff-diff.el (ediff-diff-options):
* doc/misc/ediff.texi (Patch and Diff Programs): Note that setting
this variable directly is probably the wrong thing to do (bug#6512).
In @code{ediff-diff-options}, it may be useful to specify options
such as @samp{-w} that ignore certain kinds of changes. However,
Ediff does not let you use the option @samp{-c}, as it doesn't recognize this
-format yet.
+format yet. (If you alter this variable, it should be done via the
+Customize interface instead of using @code{setq} directly.)
@item ediff-coding-system-for-read
@vindex ediff-coding-system-for-read
This variable is not for customizing the look of the differences produced by
the command \\[ediff-show-diff-output]. Use the variable
-`ediff-custom-diff-options' for that."
+`ediff-custom-diff-options' for that.
+
+Setting this variable directly may not yield the expected
+results. It should be set via the Customize interface instead."
:set #'ediff-set-diff-options
:type 'string)