cmd-generate-release-meta: propagate FCOS stream name from label

We need the stream name there. It was previously getting that from the
git branch name, but we don't populate that anymore in the buildah path,
only the git URL and commit. But we do have the more explicit stream
name as a label anyway, so let's use that.

Author: jlebon

src/cmd-generate-release-meta

@@ -122,7 +122,12 @@ def append_build(out, input_):
     if args.stream_name:
         streamnamesrc = {'branch': args.stream_name}
     else:
-        streamnamesrc = input_.get('coreos-assembler.container-config-git')
+        fcos_stream = input_.get('coreos-assembler.oci-imported-labels', {}).get('fedora-coreos.stream')
+        if fcos_stream:
+            streamnamesrc = {'branch': fcos_stream}
+        else:
+            streamnamesrc = input_.get('coreos-assembler.container-config-git')
+
     ensure_dup(streamnamesrc, out, 'branch', 'stream')
 
     def artifact(i):