updater: Add Commmand class to manage BBOTA commands.

Move the commands map parsing out of PerformBlockImageUpdate(), as this
can be done more easily by the caller.

The goal (not done in this CL) is to decouple command parsing logic from
the performers. This allows (a) focusing on the command logic in the
performer; and (b) extending BBOTA commands syntax separately.

Test: Run recovery_unit_test and recovery_component_test.
Change-Id: Ife202398a7660b152d84a3ba17b90f93d19c55f2
diff --git a/updater/include/private/commands.h b/updater/include/private/commands.h
new file mode 100644
index 0000000..b360000
--- /dev/null
+++ b/updater/include/private/commands.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <string>
+
+struct Command {
+  enum class Type {
+    ZERO,
+    NEW,
+    ERASE,
+    MOVE,
+    BSDIFF,
+    IMGDIFF,
+    STASH,
+    FREE,
+    LAST,  // Not a valid type.
+  };
+
+  static Type ParseType(const std::string& type_str);
+};