CodingStyle: add information about trailing whitespace

Signed-off-by: NJosh Triplett <josh@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/CodingStyle

@@ -218,6 +218,18 @@ no space after the prefix increment & decrement unary operators:
 
 and no space around the '.' and "->" structure member operators.
 
+Do not leave trailing whitespace at the ends of lines.  Some editors with
+"smart" indentation will insert whitespace at the beginning of new lines as
+appropriate, so you can start typing the next line of code right away.
+However, some such editors do not remove the whitespace if you end up not
+putting a line of code there, such as if you leave a blank line.  As a result,
+you end up with lines containing trailing whitespace.
+
+Git will warn you about patches that introduce trailing whitespace, and can
+optionally strip the trailing whitespace for you; however, if applying a series
+of patches, this may make later patches in the series fail by changing their
+context lines.
+
 
 		Chapter 4: Naming