Honour useful options from‘diff’command in‘pipe-patches’command.

  affects bzr-pipeline

Reported by Ben Finney in Debian against bzr-pipeline:
> The apparent purpose of the ‘pipeline’ plugin is to allow generating
> patches, in a more organised fashion than using ‘diff’ for each patch.
>
> In that case, the following options to the Bazaar ‘diff’ command
> should also be supported by ‘pipe-patches’:
>
> -p ARG, --prefix=ARG Set prefixes added to old and new filenames, as two
> values separated by a colon. (eg "old/:new/").
> --diff-options=ARG Pass these options to the external diff program.
>
> These would allow control over the generated patch files, presumably
> using existing functionality in Bazaar.
>
>
> -- System Information:
> Debian Release: squeeze/sid
> APT prefers testing
> APT policy: (990, 'testing'), (900, 'stable')
> Architecture: powerpc (ppc64)
>
> Kernel: Linux 2.6.32-trunk-powerpc64 (SMP w/2 CPU cores)
> Locale: LANG=en_AU.UTF-8, LC_CTYPE=en_AU.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_AU.UTF-8)
> Shell: /bin/sh linked to /bin/dash
>
> Versions of packages bzr-pipeline depends on:
> ii bzr 2.1.0-1 easy to use distributed version co
> ii python 2.5.4-9 An interactive high-level object-o
> ii python-central 0.6.14+nmu2 register and build utility for Pyt
>
> bzr-pipeline recommends no packages.
>
> bzr-pipeline suggests no packages.
>
> -- no debconf information