[git_cl] Extract helper methods

Change-Id: I6fd49699a7046d7f689ef59bf35d3d2a62c7438d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5689681
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Commit-Queue: Allen Li <ayatane@chromium.org>

git_cl.py

@@ -3694,9 +3694,16 @@ class GitAuthConfigChanger(object):
     def apply(self):
         """Apply config changes."""
         logging.debug('Configuring current Git repo authentication...')
-        cwd: str = os.getcwd()
 
-        # Credential helper
+        self._apply_cred_helper()
+        self._apply_sso()
+
+        # Override potential global gitcookie config
+        scm.GIT.SetConfig(cwd, 'http.gitcookies', '', modify_all=True)
+
+    def _apply_cred_helper(self):
+        """Apply config changes relating to credential helper."""
+        cwd: str = os.getcwd()
         if self._should_use_sso:
             scm.GIT.SetConfig(cwd,
                               f'credential.{self._base_url}.helper',
@@ -3712,6 +3719,9 @@ class GitAuthConfigChanger(object):
                               'luci',
                               append=True)
 
+    def _apply_sso(self):
+        """Apply config changes relating to SSO."""
+        cwd: str = os.getcwd()
         # SSO
         if self._should_use_sso:
             scm.GIT.SetConfig(cwd, 'protocol.sso.allow', 'always')
@@ -3726,9 +3736,6 @@ class GitAuthConfigChanger(object):
                               None,
                               modify_all=True)
 
-        # Override potential global gitcookie config
-        scm.GIT.SetConfig(cwd, 'http.gitcookies', '', modify_all=True)
-
 
 class _GitCookiesChecker(object):
     """Provides facilities for validating and suggesting fixes to .gitcookies."""