inputs/org.osbuild.containers: Drop format and file options

We hardcode oci-archive for now and use the first file in the pipeline
tree as the archive. Long term we may want to get this info from the
metadata of the oci-archive stage instead.

inputs/org.osbuild.containers

@@ -2,7 +2,8 @@
 """Inputs for container images
 
 This reads images from the `org.osbuild.containers` directory in the
-sources store.
+sources store, or from oci-archive files in pipelines (typically
+created by `org.osbuild.oci-archive`).
 
 The store is indexed by the "container image id", which is the digest
 of the container configuration file (rather than the outer manifest)
@@ -11,6 +12,9 @@ is installed. This digest is stable as opposed to the manifest digest
 which can change during transfer and storage due to
 e.g. recompression.
 
+When using pipeline sources, the first file (alphabetically) in the
+root of the tree is used as the oci archive file to install.
+
 """
 
 import os
@@ -51,19 +55,11 @@ SCHEMA = r"""
   "pipeline-options": {
     "type": "object",
     "additionalProperties": false,
-    "required": ["name", "file", "format"],
+    "required": ["name"],
     "properties": {
       "name": {
         "type": "string",
         "description": "The name to use for the image"
-      },
-      "file": {
-        "description": "File to access with in a pipeline",
-        "type": "string"
-      },
-      "format": {
-        "description": "Container archive format",
-        "enum": ["oci-archive", "docker-archive"]
       }
     }
   },
@@ -134,17 +130,19 @@ class ContainersInput(inputs.InputService):
 
     @staticmethod
     def map_pipeline_ref(store, ref, data, target):
-        filepath = data["file"].lstrip("/")
-        container_format = data["format"]
-
         # prepare the mount point
-        filename = pathlib.Path(target, filepath)
-        os.makedirs(filename.parent, exist_ok=True)
-        filename.touch()
+        os.makedirs(target, exist_ok=True)
+        print("target", target)
 
-        store.read_tree_at(ref, filename, filepath)
+        store.read_tree_at(ref, target)
 
-        return filepath, container_format
+        # Find the archive file in target, we use the first alphabetical regular file
+        files = sorted(filter(lambda f: os.path.isfile(os.path.join(target, f)),
+                              os.listdir(target)))
+        if len(files) == 0:
+            raise RuntimeError("No archive files in source")
+
+        return files[0], "oci-archive"
 
     def map(self, store, origin, refs, target, _options):
         source = store.source("org.osbuild.containers")