Move GenerateDiff into a common function.

tests/scm_unittest.py

Index: tests/scm_unittest.py
diff --git a/tests/scm_unittest.py b/tests/scm_unittest.py
index fc05677405b6d929acb3baea80f39956d3ee9228..27696f73b810c24debe47ab47ab3c2306b978194 100755
--- a/tests/scm_unittest.py
+++ b/tests/scm_unittest.py
@@ -25,7 +25,8 @@ class RootTestCase(BaseSCMTestCase):
     self.mox.ReplayAll()
     members = [
         'GIT', 'SVN',
-        'gclient_utils', 'os', 're', 'subprocess', 'sys', 'tempfile', 'xml',
+        'gclient_utils', 'os', 're', 'shutil', 'subprocess', 'sys', 'tempfile',
+        'xml',
     ]
     # If this test fails, you should add the relevant test.
     self.compareMembers(scm, members)
@@ -115,14 +116,17 @@ from :3
   def testMembersChanged(self):
     self.mox.ReplayAll()
     members = [
-        'COMMAND', 'Capture', 'CaptureStatus', 'GetEmail',
+        'COMMAND', 'Capture', 'CaptureStatus', 'FetchUpstreamTuple',
+        'GenerateDiff', 'GetBranchRef', 'GetEmail', 'GetSVNBranch',
+        'GetUpstream', 'IsGitSvn', 'ShortBranchName'
     ]
     # If this test fails, you should add the relevant test.
     self.compareMembers(scm.GIT, members)
 
   def testGetEmail(self):
     self.mox.StubOutWithMock(scm.GIT, 'Capture')
-    scm.GIT.Capture(['config', 'user.email'], self.fake_root).AndReturn('mini@me.com')
+    scm.GIT.Capture(['config', 'user.email'], self.fake_root, error_ok=True
+                    ).AndReturn('mini@me.com')
     self.mox.ReplayAll()
     self.assertEqual(scm.GIT.GetEmail(self.fake_root), 'mini@me.com')
 
@@ -139,8 +143,8 @@ class SVNTestCase(BaseSCMTestCase):
     self.mox.ReplayAll()
     members = [
         'COMMAND', 'Capture', 'CaptureHeadRevision', 'CaptureInfo',
-        'CaptureStatus', 'DiffItem', 'GetCheckoutRoot', 'GetEmail',
-        'GetFileProperty', 'IsMoved',
+        'CaptureStatus', 'DiffItem', 'GenerateDiff', 'GetCheckoutRoot',
+        'GetEmail', 'GetFileProperty', 'IsMoved',
         'ReadSimpleAuth', 'Run', 'RunAndFilterOutput', 'RunAndGetFileList',
     ]
     # If this test fails, you should add the relevant test.