patch format

[Felix Lee]

Bernardo Innocenti <bernie@develer.com>:
> Since the latter is much more readable and more widely used in other
> projects, I wanted to check if it's ok to use it despite what the
> current documentation for contributions says.

diff -u tends to be harder to read for major changes.  Try
reading diff -u of two unrelated files that are about the same
size.  What happens is: blank lines are common, and diff is kind
of arbitrary in matching up the blank lines in the two versions,
so large chunks of code end up awkwardly interleaved in the
output.  Lines with just '{' or '}' are also common problems.
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