feat: annotate devel rocks with a grade

This commit updates the rock's internal metadata (the file /.rock/metadata.yaml)
with an extra "grade: devel" key if the project's build-base is "devel". This is
to provide some amount of traceability/record that the rock was originally
created from a development base.

rockcraft/models/project.py

@@ -457,6 +457,10 @@ def generate_metadata(
             "base-digest": base_digest.hex(),
         }
 
+        if self.build_base == "devel":
+            # Annotate that this project was built with a development base.
+            metadata["grade"] = "devel"
+
         annotations = {
             "org.opencontainers.image.version": self.version,
             "org.opencontainers.image.title": self.title,

tests/spread/general/base-devel/task.yaml

@@ -8,5 +8,22 @@ execute: |
   grep placeholder-base rockcraft.orig.yaml
   sed "s/placeholder-base/$BASE/" rockcraft.orig.yaml  > rockcraft.yaml
 
-  # Build the rock & load it into docker
+  # Build the rock
   run_rockcraft pack
+
+  # Extract the built rock and check that the "grade" is "devel" in the metadata
+
+  # Extract the rock into a dir called "devel"
+  mkdir devel
+  tar -xvf base-devel*.rock -C devel
+
+  # Unpack the rootfs into "rootfs"
+  /snap/rockcraft/current/bin/umoci unpack --rootless --image devel:0.1 rootfs
+
+  # Check the grade
+  MATCH "grade: devel" < rootfs/rootfs/.rock/metadata.yaml
+
+restore: |
+  rm -rf devel
+  rm -rf rootfs
+

tests/unit/test_project.py

@@ -605,6 +605,18 @@ def test_project_generate_metadata(yaml_loaded_data):
     }
 
 
+def test_metadata_base_devel(yaml_loaded_data):
+    yaml_loaded_data["base"] = CURRENT_DEVEL_BASE
+    yaml_loaded_data["build-base"] = "devel"
+    project = Project.unmarshal(yaml_loaded_data)
+
+    now = datetime.datetime.now(datetime.timezone.utc).isoformat()
+    digest = "a1b2c3"  # mock digest
+
+    _, rock_metadata = project.generate_metadata(now, bytes.fromhex(digest))
+    assert rock_metadata["grade"] == "devel"
+
+
 EXPECTED_DUMPED_YAML = f"""\
 name: mytest
 title: My Test