Use diff.ignoreSubmodules=dirty.

With this, modified files from submodules won't be reported,
but new ones will and this makes things much faster than not
having diff.ignoreSubmodules set at all.

Bug: 1470194
Change-Id: I041b6fb3151c0b06cff3cc77d6735ad2ebe27f21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4793910
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Joanna Wang <jojwang@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Auto-Submit: Joanna Wang <jojwang@chromium.org>

gclient_scm.py

@@ -583,9 +583,9 @@ class GitWrapper(SCMWrapper):
         config = subprocess2.capture(
             ['git', 'config', '-l'],
             cwd=args[0].checkout_path).decode('utf-8').strip().splitlines()
-        if 'diff.ignoresubmodules=all' in config:
+        if 'diff.ignoresubmodules=dirty' not in config:
           subprocess2.capture(
-              ['git', 'config', '--unset', 'diff.ignoreSubmodules'],
+              ['git', 'config', 'diff.ignoreSubmodules', 'dirty'],
               cwd=args[0].checkout_path)
         if 'fetch.recursesubmodules=off' not in config:
           subprocess2.capture(

tests/gclient_scm_test.py

@@ -407,31 +407,17 @@ class ManagedGitWrapperTestCase(BaseGitWrapperTestCase):
     scm = gclient_scm.GitWrapper(self.url, self.root_dir,
                                  self.relpath)
     file_list = []
-    scm._Capture(['config', 'diff.ignoreSubmodules', 'all'])
 
     scm.update(options, (), file_list)
     self.assertEqual(file_list, expected_file_list)
     self.assertEqual(scm.revinfo(options, (), None),
                       'a7142dc9f0009350b96a11f372b6ea658592aa95')
-    with self.assertRaises(Exception):
-      scm._Capture(['config', '--get', 'diff.ignoreSubmodules'])
+    self.assertEqual(scm._Capture(['config', '--get', 'diff.ignoreSubmodules']),
+                     'dirty')
     self.assertEqual(
         scm._Capture(['config', '--get', 'fetch.recurseSubmodules']), 'off')
     sys.stdout.close()
 
-  def testUpdateUpdate_only_unset_ignoresubmodules_all(self):
-    if not self.enabled:
-      return
-    options = self.Options()
-    scm = gclient_scm.GitWrapper(self.url, self.root_dir, self.relpath)
-    file_list = []
-    scm._Capture(['config', 'diff.ignoreSubmodules', 'none'])
-
-    scm.update(options, (), file_list)
-    self.assertEqual(scm._Capture(['config', '--get', 'diff.ignoreSubmodules']),
-                     'none')
-    sys.stdout.close()
-
   def testUpdateMerge(self):
     if not self.enabled:
       return