osbuild: introduce manifest concept

A manifest is simply a struct containing a sources and a pipeline
object. We want to store and transfer pielines always with their
sources, and will use the manifest for this.

When serialized, a manifest can be the input to `osbuild`, just
like a bare pipeline can be. This means there will be no need
to pass in sources separately on the commandline.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/osbuild/osbuild.go

@@ -2,6 +2,12 @@
 // OSBuild types.
 package osbuild
 
+// A Manifest represents an OSBuild source and pipeline manifest
+type Manifest struct {
+	Sources  Sources  `json:"sources"`
+	Pipeline Pipeline `json:"pipeline"`
+}
+
 // A Pipeline represents an OSBuild pipeline
 type Pipeline struct {
 	// The build environment which can run this pipeline