View source for Submit a patch

Unpack the latest tarball which creates a tree with e.g. the top-level directory plplot-5.9.0

cp -a plplot-5.9.0 plplot-5.9.0new

Make your changes in the correct location in plplot-5.9.0new overwriting some of the files and adding new files in some cases.  
You should not compile anything in either plplot-5.9.0 or plplot-5.9.0new. That is, both should be clean directory trees. In order to test your changes make sure you configure plplot with CMake out-of-source. E.g.
plplot-5.5.3new:

cp -a plplot-5.5.3new plplot-5.5.3_working
cd plplot-5.5.3_working
./configure --enable-wxwidgets, etc.

To produce the requested patch from the two clean directory trees set up
above do the following:

diff -Naur plplot-5.5.3 plplot-5.5.3new >plplot-5.5.3.patch

Please review plplot-5.5.3.patch to make sure those are the exact changes to
the main tree that you require and nothing extra.  Afterwards do the
following:

gzip plplot-5.5.3.patch

Send plplot-5.5.3.patch.gz (the file created by gzip) to me.