Update instrucitons on regenerating patches

README.rst

 naclports - Ports of open source software to Native Client
 ==========================================================
 
 naclports is collection of open source libraries and applications that have
 been ported to Native Client, along with set to tools for building and
 maintaining them.
 
 Packages can be built from source or prebuilt binaries packages can be
 downloaded from the continuous build system.
 
@@ skipping 202 matching lines @@
 run ``shellcheck`` to catch common errors.  The recommended command line
 for this is::
 
   shellcheck -e SC2044,SC2129,SC2046,SC2035,SC2034,SC2086,SC2148 \
     `git ls-files "*.sh"`
 
 Modifying package sources / Working with patches
 ------------------------------------------------
 
 When a package is first built, its source is downloaded and extracted to
-``out/build/<PKG_NAME>``. A new git repository is then created in this
+``out/build/<pkg_name>``. A new git repository is then created in this
 folder with the original archive contents on a branch called ``upstream``. The
 optional ``nacl.patch`` file is then applied on the ``master`` branch. This
 means that at any given time you can see the changes from upstream using ``git
 diff upstream``.
 
 To make changes to a package's patch file the recommended workflow is:
 
-1. Directly modify the sources in ``out/build/PKG_NAME``.
+1. Directly modify the sources in ``out/build/<pkg_name>``.
 2. Build the package and verify the changes.
-3. Use ``git diff upstream.. > ../path/to/nacl.patch`` to regenerate
-   the patch file.
+3. Use ``naclpors updatepatch <pkg_name>`` to (re)generate the patch file.
 
 Whenever the upstream archive or patch file changes and you try to build the
 package you will be prompted to remove the existing repository and start a new
-one. This is to avoid deleting a repository that might have unsaved changed.
+one. This is to avoid deleting a repository that might contain unsaved changed.
 
 Happy porting!