NEWS.md: update for osbuild version 15

Major changes are the new assembler, support for passing client
certificates to access Red Hat content in the files source and
the shiny new ManifestPreProcessor.

NEWS.md

@@ -1,5 +1,47 @@
 # OSBuild - Build-Pipelines for Operating System Artifacts
 
+## CHANGES WITH 15:
+
+  * New assembler, `org.osbuild.oci-archive`, that will turn a tree
+    into an Open Container Initiative Image compliant archive. These
+    can be used to run containers via e.g. podman.
+
+  * Support for client side certificates to download content from the
+    Red Hat servers: the `org.osbuild.files` source got support for
+    reading entitlements and pass those certificates along when doing
+    requests to fetch the files, i.e. RPMs.
+
+  * A new ManifestPreProcessor (MPP) was added as a new tool, located
+    in `tools/mpp-depsolve.py`. Currently, it can take an existing
+    manifest and dep-solve packages specified via a new  `mpp-depsolve`
+    options in existing `org.osbuild.rpm` stages.
+    This is now used to generate Fedora 32 based test pipelines.
+
+  * The `org.osbuild.ostree.commit` assembler gained to option to produce
+    a tarball archive instead of the emitting the plain OSTree repository.
+
+  * Schema validation is now done with the draft 4 validator, and works
+    therefore with pyhthon-jsonschema 2.6.
+
+  * The `tree_id` and `outpud_id` fields got drop from when inspecting
+    pipelines via `osbuild --inspect`.
+
+  * The `--build-env` option has been dropped from the command line
+    interface. It was deprecated and not used anymore.
+
+  * Tests have been converted to not rely on `tree_id` and `output_id`
+    anymore, as they are deprecated and will be removed in the future.
+
+  * Lots of other improvements to the test infrastructure and the CI.
+
+  * And finally for something meta: this file has been re-formatted to be
+    proper markdown.
+
+Contributions from: Christian Kellner, David Rheinsberg, Jacob Kozol,
+                    Major Hayden
+
+— Berlin, 2020-05-20
+
 ## CHANGES WITH 14:
 
   * Schema validation: The osbuild python library gained support for