cros_util: fix up naming

Since these two scripts are tracking upstream Chrome OS repos,
fixing naming is a bit harder. This patch creates a variable to
hold the name of the main branch, so it's easier to fix these
files in case any future name fixing on upstream.

Also run `yapf` during presubmit.

BUG=chromium:1099035
TEST=None

Change-Id: Ic72a213dadf12b382a76fe50d48cde6fcecc3b25
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2270728
Reviewed-by: Caroline Tice <cmtice@chromium.org>
Commit-Queue: Tiancong Wang <tcwang@google.com>
Tested-by: Tiancong Wang <tcwang@google.com>
diff --git a/cros_utils/manifest_versions.py b/cros_utils/manifest_versions.py
index 115c604..4838de3 100644
--- a/cros_utils/manifest_versions.py
+++ b/cros_utils/manifest_versions.py
@@ -19,6 +19,8 @@
 from cros_utils import command_executer
 from cros_utils import logger
 
+MANIFEST_VERSION_MAIN_BRANCH = 'master'
+
 
 def IsCrosVersion(version):
   match = re.search(r'(\d+\.\d+\.\d+\.\d+)', version)
@@ -72,7 +74,8 @@
     commands = [
         'cd {0}'.format(self.clone_location), 'cd manifest-versions',
         'git checkout -f $(git rev-list' +
-        ' --max-count=1 --before={0} origin/master)'.format(my_time)
+        ' --max-count=1 --before={0} origin/{1})'.format(
+            my_time, MANIFEST_VERSION_MAIN_BRANCH)
     ]
     ret = self.ce.RunCommands(commands)
     if ret:
@@ -106,7 +109,7 @@
       version = pp[-2] + '.' + small
     commands = [
         'cd {0}'.format(self.clone_location), 'cd manifest-versions',
-        'git checkout master'
+        'git checkout {0}'.format(MANIFEST_VERSION_MAIN_BRANCH)
     ]
     self.ce.RunCommands(commands)
     return version
@@ -120,7 +123,8 @@
     commands = [
         'cd {0}'.format(self.clone_location), 'cd manifest-versions',
         'git checkout -f $(git rev-list' +
-        ' --max-count=1 --before={0} origin/master)'.format(my_time)
+        ' --max-count=1 --before={0} origin/{1})'.format(
+            my_time, MANIFEST_VERSION_MAIN_BRANCH)
     ]
     ret = self.ce.RunCommands(commands)
     if ret:
@@ -133,7 +137,7 @@
     version = pp[-2] + '.' + small
     commands = [
         'cd {0}'.format(self.clone_location), 'cd manifest-versions',
-        'git checkout master'
+        'git checkout {0}'.format(MANIFEST_VERSION_MAIN_BRANCH)
     ]
     self.ce.RunCommands(commands)
     return version
diff --git a/cros_utils/misc.py b/cros_utils/misc.py
index b4beb60..d8b47d1 100644
--- a/cros_utils/misc.py
+++ b/cros_utils/misc.py
@@ -24,6 +24,8 @@
 TOOLCHAIN_UTILS_PATH = ('/mnt/host/source/src/third_party/toolchain-utils/'
                         'cros_utils/toolchain_utils.sh')
 
+CROS_MAIN_BRANCH = 'cros/master'
+
 
 def GetChromeOSVersionFromLSBVersion(lsb_version):
   """Get Chromeos version from Lsb version."""
@@ -444,8 +446,9 @@
       cmd1, print_to_console=True) == 0
 
 
-def ApplyGerritPatches(chromeos_root, gerrit_patch_string,
-                       branch='cros/master'):
+def ApplyGerritPatches(chromeos_root,
+                       gerrit_patch_string,
+                       branch=CROS_MAIN_BRANCH):
   """Apply gerrit patches on a chromeos tree.
 
   Args: