Hi. Here's a patch to add a new function to diff-mode:
(diff-refresh-hunk). I'm binding it to "C-c C-l" because it "refreshes"
the hunk like C-l refreshes the screen. This is useful to me to throw
out no-op pieces of a hunk, which I often get after editing the
*vc-diff* buffer.

For instance, I might end up with this hunk:

@@ -298,12 +312,12 @@
         stuff
-        f(x);
+           f(x);
 
         more stuff

-        g(x);
+        g(x);

         stuff

I'd like to clean it up by throwing out the g(x) pieces, since they're
the same, but keeping the f(x) pieces since they differ. C-c C-w would
throw out both since it ignores whitespace differences, but the new C-c
C-l does what I want.

Thanks