_artifact.py: Store additional metadata on the artifact

This commit enriches the metadata we store on artifacts in the
new detatched low/high diversity metadata files:

  * The SandboxConfig is now stored in the artifact, allowing
    one to perform activities such as launching sandboxes on
    artifacts downloaded via artifact name (without backing
    project data).

  * The environment variables is now stored in the artifact,
    similarly allowing one to shell into a downloaded artifacts
    which are unrelated to a loaded project.

  * The element variables are now stored in the artifact, allowing
    more flexibility in what the core can do with a downloaded
    ArtifactElement

  * The element's strict key

All of these of course can additionally enhance traceability
in the UI with commands such as `bst artifact show`.

Summary of changes:

  * _artifact.py:

    - Store new data in the new proto digests.
    - Added new accessors to extract these new aspects from loaded artifacts.
    - Bump the proto version number for compatibility

  * _artifactcache.py: Adjusted to push and pull the new blobs and digests.

  * element.py:

    - Call Artifact.cache() with new parameters
    - Expect the strict key from Artifact.get_meta_keys()
    - Always specify the strict key when constructing an Artifact
      instance which will later be used to cache the artifact
      (i.e. the self.__artifact Artifact).

  * _versions.py: Bump the global artifact version number, as this breaks
    the artifact format.

  * tests/cachekey: Updated cache key test for new keys.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/buildstream/_artifactcache.py b/src/buildstream/_artifactcache.py
index 5ccdf8fd8..c3d96166c 100644
--- a/src/buildstream/_artifactcache.py
+++ b/src/buildstream/_artifactcache.py
@@ -404,7 +404,7 @@ class ArtifactCache(AssetCache):
                 except FileNotFoundError:
                     pass
 
-            digests = [artifact_digest]
+            digests = [artifact_digest, artifact_proto.low_diversity_meta, artifact_proto.high_diversity_meta]
 
             if str(artifact_proto.public_data):
                 digests.append(artifact_proto.public_data)
@@ -470,7 +470,9 @@ class ArtifactCache(AssetCache):
         if artifact_proto.sources:
             referenced_directories.append(artifact_proto.sources)
 
-        referenced_blobs = [log_file.digest for log_file in artifact_proto.logs]
+        referenced_blobs = [artifact_proto.low_diversity_meta, artifact_proto.high_diversity_meta] + [
+            log_file.digest for log_file in artifact_proto.logs
+        ]
 
         try:
             remote.push_blob(
@@ -530,7 +532,7 @@ class ArtifactCache(AssetCache):
             if pull_buildtrees and str(artifact.buildtree):
                 __pull_digest(artifact.buildtree)
 
-            digests = []
+            digests = [artifact.low_diversity_meta, artifact.high_diversity_meta]
             if str(artifact.public_data):
                 digests.append(artifact.public_data)