Adds new merge builds script for use in merging two non-dist builds.

Bug: 137853921
Test: python -m unittest test_common
Test: python -m unittest test_merge_target_files
Test: Built two partial builds without dist. Ran out/host/linux-x86/bin/merge_builds.
Flashed using `fastboot flashall`. Device boots.
Change-Id: Iffd0a447cdf19a7775a813b4b896178aa6f861f3
diff --git a/tools/releasetools/merge_builds.py b/tools/releasetools/merge_builds.py
new file mode 100644
index 0000000..7724d6f
--- /dev/null
+++ b/tools/releasetools/merge_builds.py
@@ -0,0 +1,138 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2019 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.
+#
+"""Merges two non-dist partial builds together.
+
+Given two partial builds, a framework build and a vendor build, merge the builds
+together so that the images can be flashed using 'fastboot flashall'.
+
+To support both DAP and non-DAP vendor builds with a single framework partial
+build, the framework partial build should always be built with DAP enabled. The
+vendor partial build determines whether the merged result supports DAP.
+
+This script does not require builds to be built with 'make dist'.
+This script assumes that images other than super_empty.img do not require
+regeneration, including vbmeta images.
+TODO(b/137853921): Add support for regenerating vbmeta images.
+
+Usage: merge_builds.py [args]
+
+  --framework_images comma_separated_image_list
+      Comma-separated list of image names that should come from the framework
+      build.
+
+  --product_out_framework product_out_framework_path
+      Path to out/target/product/<framework build>.
+
+  --product_out_vendor product_out_vendor_path
+      Path to out/target/product/<vendor build>.
+"""
+from __future__ import print_function
+
+import logging
+import os
+import sys
+
+import build_super_image
+import common
+
+logger = logging.getLogger(__name__)
+
+OPTIONS = common.OPTIONS
+OPTIONS.framework_images = ("system",)
+OPTIONS.product_out_framework = None
+OPTIONS.product_out_vendor = None
+
+
+def CreateImageSymlinks():
+  for image in OPTIONS.framework_images:
+    image_path = os.path.join(OPTIONS.product_out_framework, "%s.img" % image)
+    symlink_path = os.path.join(OPTIONS.product_out_vendor, "%s.img" % image)
+    if os.path.exists(symlink_path):
+      if os.path.islink(symlink_path):
+        os.remove(symlink_path)
+      else:
+        raise ValueError("Attempting to overwrite built image: %s" %
+                         symlink_path)
+    os.symlink(image_path, symlink_path)
+
+
+def BuildSuperEmpty():
+  framework_dict = common.LoadDictionaryFromFile(
+      os.path.join(OPTIONS.product_out_framework, "misc_info.txt"))
+  vendor_dict = common.LoadDictionaryFromFile(
+      os.path.join(OPTIONS.product_out_vendor, "misc_info.txt"))
+  # Regenerate super_empty.img if both partial builds enable DAP. If only the
+  # the vendor build enables DAP, the vendor build's existing super_empty.img
+  # will be reused. If only the framework build should enable DAP, super_empty
+  # should be included in the --framework_images flag to copy the existing
+  # super_empty.img from the framework build.
+  if (framework_dict.get("use_dynamic_partitions") == "true") and (
+      vendor_dict.get("use_dynamic_partitions") == "true"):
+    merged_dict = dict(vendor_dict)
+    merged_dict.update(
+        common.MergeDynamicPartitionInfoDicts(
+            framework_dict=framework_dict,
+            vendor_dict=vendor_dict,
+            size_prefix="super_",
+            size_suffix="_group_size",
+            list_prefix="super_",
+            list_suffix="_partition_list"))
+    output_super_empty_path = os.path.join(OPTIONS.product_out_vendor,
+                                           "super_empty.img")
+    build_super_image.BuildSuperImage(merged_dict, output_super_empty_path)
+
+
+def MergeBuilds():
+  CreateImageSymlinks()
+  BuildSuperEmpty()
+  # TODO(b/137853921): Add support for regenerating vbmeta images.
+
+
+def main():
+  common.InitLogging()
+
+  def option_handler(o, a):
+    if o == "--framework_images":
+      OPTIONS.framework_images = [i.strip() for i in a.split(",")]
+    elif o == "--product_out_framework":
+      OPTIONS.product_out_framework = a
+    elif o == "--product_out_vendor":
+      OPTIONS.product_out_vendor = a
+    else:
+      return False
+    return True
+
+  args = common.ParseOptions(
+      sys.argv[1:],
+      __doc__,
+      extra_long_opts=[
+          "framework_images=",
+          "product_out_framework=",
+          "product_out_vendor=",
+      ],
+      extra_option_handler=option_handler)
+
+  if (args or OPTIONS.product_out_framework is None or
+      OPTIONS.product_out_vendor is None):
+    common.Usage(__doc__)
+    sys.exit(1)
+
+  MergeBuilds()
+
+
+if __name__ == "__main__":
+  main()