CONTRIBUTING.md: Mention contribution rules and coding style

CONTRIBUTING.md

@@ -0,0 +1,35 @@
+# p11-kit -- Information about our contribution rules and coding style
+
+# Test suite
+
+New functionality should be accompanied by a test case which verifies
+the correctness of p11-kit's operation on successful use of the new
+functionality, as well as on failure cases.  The p11-kit test suite is
+run on "ninja test" if you use meson for building, or on "make check"
+if you use autotools.
+
+Bug fixes should also come with a test case that exercises the code
+path that previously failed to operate.  This prevents future
+regressions.
+
+# Coding style
+
+In general, use [the Linux kernel coding
+style](https://www.kernel.org/doc/html/latest/process/coding-style.html),
+except that we put a space between function name and open parenthesis.
+
+# API documentation
+
+Use [gtk-doc](https://www.gtk.org/gtk-doc/) for API documentation.
+
+# Library symbol versioning
+
+We use [the libtool versioning scheme](https://www.gnu.org/software/libtool/manual/html_node/Versioning.html#Versioning) to ensure ABI compatibility.  If you add a new API function, update [libp11-kit.map](https://github.com/p11-glue/p11-kit/blob/master/p11-kit/libp11-kit.map) and [libp11-kit-*.dll.def](https://github.com/p11-glue/p11-kit/blob/master/p11-kit/libp11-kit-0.dll.def) accordingly.
+
+# Resources:
+
+* [Documentation on developing p11-kit](https://p11-glue.github.io/p11-glue/p11-kit/manual/devel.html)
+* [Code available at](https://github.com/p11-glue/p11-kit)
+* [General Website](https://p11-glue.github.io/p11-glue/p11-kit.html)
+* [Mailing list](https://lists.freedesktop.org/mailman/listinfo/p11-glue)
+* [Report bugs](https://github.com/p11-glue/p11-kit/issues)

Makefile.am

@@ -22,7 +22,7 @@ BUILT_SOURCES =
 
 CLEANFILES =
 
-EXTRA_DIST = HACKING meson.build meson_options.txt po/meson.build \
+EXTRA_DIST = CONTRIBUTING.md meson.build meson_options.txt po/meson.build \
 	doc/manual/meson.build doc/manual/userdir.xml.in \
 	doc/manual/sysdir.xml.in doc/manual/version.xml.in \
 	bash-completion