add CONTRIBUTING

CONTRIBUTING.rst

+CONTRIBUTING
+============
+
+To contribute code or documentation, submit a pull request at the
+`source repository website
+<https://code.uplex.de/uplex-varnish/libvmod-blobdigest>`_.
+
+If you have a problem or discover a bug, you can post an `issue
+<https://code.uplex.de/uplex-varnish/libvmod-blobdigest/issues>`_ at
+the website. You can also write to <varnish-support@uplex.de>.
+
+For developers
+--------------
+
+The build specifies C99 conformance, all compiler warnings turned on,
+and all warnings considered errors (compiler options ``-std=c99
+-Werror -Wall``).
+
+By default, ``CFLAGS`` is set to ``-g -O2``, so that symbols are
+included in the shared library, and optimization is at level
+``O2``. To change or disable these options, set ``CFLAGS`` explicitly
+before calling ``make`` (it may be set to the empty string).
+
+For development/debugging cycles, the ``configure`` option
+``--enable-debugging`` is recommended (off by default). This will turn
+off optimizations and function inlining, so that a debugger will step
+through the code as expected.
+
+* source repository: https://code.uplex.de/uplex-varnish/libvmod-blobdigest

README.rst

@@ -169,6 +169,13 @@ INSTALLATION
 
 See `INSTALL.rst <INSTALL.rst>`_ in the source repository.
 
+CONTRIBUTING
+============
+
+See `CONTRIBUTING.rst <CONTRIBUTING.rst>`_ in the source repository
+for notes on contributing source code and documentation, raising
+issues, and for developer guidelines.
+
 SEE ALSO
 ========
 

src/vmod_blobdigest.vcc

@@ -126,6 +126,13 @@ INSTALLATION
 
 See `INSTALL.rst <INSTALL.rst>`_ in the source repository.
 
+CONTRIBUTING
+============
+
+See `CONTRIBUTING.rst <CONTRIBUTING.rst>`_ in the source repository
+for notes on contributing source code and documentation, raising
+issues, and for developer guidelines.
+
 SEE ALSO
 ========