Added some tips to the contributor docs, namely about removing traili…

…ng whitespaces and about mentioning relevant ticket numbers in tests.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16688 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/internals/contributing/writing-code/coding-style.txt

@@ -184,6 +184,12 @@ Miscellaneous
     * Remove ``import`` statements that are no longer used when you change code.
       The most common tools for this task are `pyflakes`_ and `pylint`_.
 
+    * Systematically remove all trailing whitespaces from your code as those
+      add unnecessary bytes, add visual clutter to the patches and can also
+      occasionally cause unnecessary merge conflicts. Some IDE's can be
+      configured to automatically remove them and most VCS tools can be set to
+      highlight them in diff outputs.
+
     * Please don't put your name in the code you contribute. Our policy is to
       keep contributors' names in the ``AUTHORS`` file distributed with Django
       -- not scattered throughout the codebase itself. Feel free to include a

docs/internals/contributing/writing-code/submitting-patches.txt

@@ -101,8 +101,11 @@ Patch style
 
     * The code required to fix a problem or add a feature is an essential part
       of a patch, but it is not the only part. A good patch should also
-      include a regression test to validate the behavior that has been fixed,
-      to prevent the problem from arising again.
+      include a regression test to validate the behavior that has been fixed
+      and to prevent the problem from arising again. Also, if some tickets are
+      relevant to the code that you've written, mention the ticket numbers in
+      some comments in the test so that one can easily trace back the relevant
+      discussions after your patch gets committed and the tickets get closed.
 
     * If the code associated with a patch adds a new feature, or modifies
       behavior of an existing feature, the patch should also contain