Relnotes: decribe the updates to the "text=auto" attribute

Helped-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/RelNotes/2.10.0.txt

@@ -235,6 +235,15 @@ Performance, Internal Implementation, Development Support etc.
  * The API to iterate over all the refs (i.e. for_each_ref(), etc.)
    has been revamped.
 
+ * The handling of the "text = auto" attribute has been updated.
+   $ echo "* text=auto eol=crlf" >.gitattributes
+   used to have the same effect as
+   $ echo "* text=auto eol=crlf" >.gitattributes
+   $ git config core.eol crlf
+   i.e. declaring all files are text; the combination now is
+   equivalent to doing
+   $ git config core.autocrlf true
+
  * A few tests that specifically target "git rebase -i" have been
    added.