* doc/lispref/text.texi (Changing Properties): Document
with-silent-modifications (bug#21171).
@code{buffer-substring-no-properties}, which copies text from the
buffer but does not copy its properties.
+@findex with-silent-modifications
+ If you wish to add or remove text properties to a buffer without
+marking the buffer as modified, you can wrap the calls above in the
+@code{with-silent-modifications} macro.
+
@node Property Search
@subsection Text Property Search Functions
@cindex searching text properties