More changes for registry-v2 in python.

Implement the minimal changes to the local filesystem storage driver and feed them through the distributed storage driver.
Create a digest package which contains digest_tools and checksums.
Fix the tests to use the new v1 endpoint locations.
Fix repository.delete_instance to properly filter the generated queries to avoid most subquery deletes, but still generate them when not explicitly filtered.

endpoints/v2/blob.py

@@ -0,0 +1,77 @@
+import logging
+
+from flask import make_response, url_for, request
+
+import data.model.blob
+
+from app import storage
+from digest import digest_tools
+from endpoints.v2 import v2_bp, require_repo_read, require_repo_write, get_input_stream
+from auth.jwt_auth import process_jwt_auth
+from endpoints.decorators import anon_protect
+from util.http import abort
+
+
+logger = logging.getLogger(__name__)
+
+
+@v2_bp.route('/<namespace>/<repo_name>/blobs/<regex("' + digest_tools.DIGEST_PATTERN + '"):digest>',
+             methods=['HEAD'])
+@process_jwt_auth
+@require_repo_read
+@anon_protect
+def check_blob_existence(namespace, repo_name, digest):
+  try:
+    found = data.model.blob.get_blob_by_digest(digest)
+
+    # The response body must be empty for a successful HEAD request
+    return make_response('')
+  except data.model.blob.BlobDoesNotExist:
+    abort(404)
+
+
+@v2_bp.route('/<namespace>/<repo_name>/blobs/<regex("' + digest_tools.DIGEST_PATTERN + '"):digest>',
+             methods=['GET'])
+@process_jwt_auth
+@require_repo_read
+@anon_protect
+def download_blob(namespace, repo_name, digest):
+  return make_response('')
+
+
+@v2_bp.route('/<namespace>/<repo_name>/blobs/uploads/', methods=['POST'])
+@process_jwt_auth
+@require_repo_write
+@anon_protect
+def start_blob_upload(namespace, repo_name):
+  new_upload_uuid = storage.initiate_chunked_upload(storage.preferred_locations[0])
+  accepted = make_response('', 202)
+  accepted.headers['Location'] = url_for('v2.upload_chunk', namespace=namespace,
+                                         repo_name=repo_name, upload_uuid=new_upload_uuid)
+  accepted.headers['Range'] = 'bytes=0-0'
+  accepted.headers['Docker-Upload-UUID'] = new_upload_uuid
+  return accepted
+
+
+@v2_bp.route('/<namespace>/<repo_name>/blobs/uploads/<upload_uuid>', methods=['PUT'])
+@process_jwt_auth
+@require_repo_write
+@anon_protect
+def upload_chunk(namespace, repo_name, upload_uuid):
+  digest = request.args.get('digest', None)
+  upload_location = storage.preferred_locations[0]
+  bytes_written = storage.stream_upload_chunk(upload_location, upload_uuid, 0, -1,
+                                              get_input_stream(request))
+
+  if digest is not None:
+    final_blob_location = digest_tools.content_path(digest)
+    storage.complete_chunked_upload(upload_location, upload_uuid, final_blob_location, digest)
+    data.model.blob.store_blob_record(digest, upload_location)
+
+    response = make_response('', 201)
+    response.headers['Docker-Content-Digest'] = digest
+    response.headers['Location'] = url_for('v2.download_blob', namespace=namespace,
+                                           repo_name=repo_name, digest=digest)
+    return response
+
+  return make_response('', 202)