Fixed #17334 - Documented the commit message style for backports; thanks krzysiumed for the draft patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17294 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/internals/contributing/committing-code.txt

@@ -91,6 +91,18 @@ repository:
   Subversion and Trac so that any commit message in that format will
   automatically post a comment to the appropriate ticket.
 
+* Write commit messages for backports using this pattern::
+
+    [<Django version>] Fixed <ticket> -- <description>
+
+    Backport of <revision> from <branch>.
+
+  For example::
+
+    [1.3.X] Fixed #17028 - Changed diveintopython.org -> diveintopython.net.
+
+    Backport of r17115 from trunk.
+
 Reverting commits
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