feat(worker): Extend draft interface with commit metadata

Adds message, time, and renames hexsha to refs (not all refs are a hexsha)

Author: nellh

services/datalad/datalad_service/handlers/draft.py

@@ -1,3 +1,4 @@
+import datetime
 import os
 
 import falcon
@@ -19,8 +20,11 @@ async def on_get(self, req, resp, dataset):
         if dataset and os.path.exists(dataset_path):
             repo = pygit2.Repository(dataset_path)
             commit = repo.revparse_single('HEAD')
-            resp.media = {'hexsha': str(commit.id),
-                          'tree': str(commit.tree_id)}
+            resp.media = {'ref': str(commit.id),
+                          'hexsha': str(commit.id), # Deprecate 'hexsha' but retain for now
+                          'tree': str(commit.tree_id),
+                          'message': str(commit.message),
+                          'modified': datetime.datetime.fromtimestamp(commit.author.time).isoformat() + 'Z'}
             resp.status = falcon.HTTP_OK
         else:
             resp.status = falcon.HTTP_NOT_FOUND