asymmetric patch context (was: [PATCH] math/lapack patch-aa too much context?)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> pkgsrc patches should always be generated using mkpatches from
> pkgtools/pkgdiff to ensure correctness and reduced diff noise on
> changes.
That doesn't always work, see mail/dovecot/patches/patch-ab, where an option 
(managesieve) applies a sort-of-upstream patch that changes a line that would 
belong to the context if you were to generate the patch automatically.