Minor refactor tools/releasetools/common.py

- Sort the import modules in alphabetical order.
- Define module variables for avbtool arguments name.

Test: atest releasetools_test
Bug: 300604688
Change-Id: I7990b94cfc1d7b3e977ceb0a3dc2317689891229
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index a3daca5..c5a3fe7 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -20,7 +20,6 @@
 import datetime
 import errno
 import fnmatch
-from genericpath import isdir
 import getopt
 import getpass
 import gzip
@@ -34,12 +33,13 @@
 import shlex
 import shutil
 import subprocess
-import sys
 import stat
+import sys
 import tempfile
 import threading
 import time
 import zipfile
+from genericpath import isdir
 from hashlib import sha1, sha256
 
 import images
@@ -112,13 +112,18 @@
 # descriptor into vbmeta.img. When adding a new entry here, the
 # AVB_FOOTER_ARGS_BY_PARTITION in sign_target_files_apks need to be updated
 # accordingly.
-AVB_PARTITIONS = ('boot', 'init_boot', 'dtbo', 'odm', 'product', 'pvmfw', 'recovery',
-                  'system', 'system_ext', 'vendor', 'vendor_boot', 'vendor_kernel_boot',
-                  'vendor_dlkm', 'odm_dlkm', 'system_dlkm')
+AVB_PARTITIONS = ('boot', 'init_boot', 'dtbo', 'odm', 'product', 'pvmfw',
+                  'recovery', 'system', 'system_ext', 'vendor', 'vendor_boot',
+                  'vendor_kernel_boot', 'vendor_dlkm', 'odm_dlkm',
+                  'system_dlkm')
 
 # Chained VBMeta partitions.
 AVB_VBMETA_PARTITIONS = ('vbmeta_system', 'vbmeta_vendor')
 
+# avbtool arguments name
+AVB_ARG_NAME_INCLUDE_DESC_FROM_IMG = '--include_descriptors_from_image'
+AVB_ARG_NAME_CHAIN_PARTITION = '--chain_partition'
+
 # Partitions that should have their care_map added to META/care_map.pb
 PARTITIONS_WITH_CARE_MAP = [
     'system',
@@ -1467,7 +1472,7 @@
   # Check if chain partition is used.
   key_path = info_dict.get("avb_" + partition + "_key_path")
   if not key_path:
-    return ["--include_descriptors_from_image", image]
+    return [AVB_ARG_NAME_INCLUDE_DESC_FROM_IMG, image]
 
   # For a non-A/B device, we don't chain /recovery nor include its descriptor
   # into vbmeta.img. The recovery image will be configured on an independent
@@ -1479,7 +1484,7 @@
 
   # Otherwise chain the partition into vbmeta.
   chained_partition_arg = GetAvbChainedPartitionArg(partition, info_dict)
-  return ["--chain_partition", chained_partition_arg]
+  return [AVB_ARG_NAME_CHAIN_PARTITION, chained_partition_arg]
 
 
 def GetAvbChainedPartitionArg(partition, info_dict, key=None):
@@ -1598,7 +1603,7 @@
       # same location when running this script (we have the input target_files
       # zip only). For such cases, we additionally scan other locations (e.g.
       # IMAGES/, RADIO/, etc) before bailing out.
-      if arg == '--include_descriptors_from_image':
+      if arg == AVB_ARG_NAME_INCLUDE_DESC_FROM_IMG:
         chained_image = split_args[index + 1]
         if os.path.exists(chained_image):
           continue
diff --git a/tools/releasetools/test_common.py b/tools/releasetools/test_common.py
index c69a13d..2bd4f36 100644
--- a/tools/releasetools/test_common.py
+++ b/tools/releasetools/test_common.py
@@ -1585,7 +1585,8 @@
     info_dict = {}
     cmd = common.GetAvbPartitionArg('system', '/path/to/system.img', info_dict)
     self.assertEqual(
-        ['--include_descriptors_from_image', '/path/to/system.img'], cmd)
+        [common.AVB_ARG_NAME_INCLUDE_DESC_FROM_IMG, '/path/to/system.img'],
+        cmd)
 
   @test_utils.SkipIfExternalToolsUnavailable()
   def test_AppendVBMetaArgsForPartition_vendorAsChainedPartition(self):
@@ -1598,7 +1599,7 @@
     }
     cmd = common.GetAvbPartitionArg('vendor', '/path/to/vendor.img', info_dict)
     self.assertEqual(2, len(cmd))
-    self.assertEqual('--chain_partition', cmd[0])
+    self.assertEqual(common.AVB_ARG_NAME_CHAIN_PARTITION, cmd[0])
     chained_partition_args = cmd[1].split(':')
     self.assertEqual(3, len(chained_partition_args))
     self.assertEqual('vendor', chained_partition_args[0])
@@ -1631,7 +1632,7 @@
     cmd = common.GetAvbPartitionArg(
         'recovery', '/path/to/recovery.img', info_dict)
     self.assertEqual(2, len(cmd))
-    self.assertEqual('--chain_partition', cmd[0])
+    self.assertEqual(common.AVB_ARG_NAME_CHAIN_PARTITION, cmd[0])
     chained_partition_args = cmd[1].split(':')
     self.assertEqual(3, len(chained_partition_args))
     self.assertEqual('recovery', chained_partition_args[0])