git-squash-branch: handle empty squashes and dirty trees

tests/git_common_test.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for git_common.py"""
 
 import binascii
 import collections
 import os
@@ skipping 543 matching lines @@
     ])
 
     self.assertEqual(bottomup, [
       ('branch_L', 'branch_K'),
       ('branch_Z', 'root_X'),
       ('branch_K', 'branch_G'),
       ('branch_G', 'root_A'),
       ('root_A', 'root_X'),
     ])
 
+  def testIsGitTreeDirty(self):
+    self.assertEquals(False, self.repo.run(self.gc.is_dirty_git_tree, 'foo'))
+    self.repo.open('test.file', 'w').write('test data')
+    self.repo.git('add', 'test.file')
+    self.assertEquals(True, self.repo.run(self.gc.is_dirty_git_tree, 'foo'))
+
   def testSquashBranch(self):
     self.repo.git('checkout', 'branch_K')
 
-    self.repo.run(self.gc.squash_current_branch, 'cool message')
+    self.assertEquals(True, self.repo.run(self.gc.squash_current_branch,
+                                          'cool message'))
 
     lines = ['cool message', '']
     for l in 'HIJK':
       lines.extend((self.repo[l], l, ''))
     lines.pop()
     msg = '\n'.join(lines)
 
     self.assertEquals(self.repo.run(self.gc.run, 'log', '-n1', '--format=%B'),
                       msg)
 
     self.assertEquals(
       self.repo.git('cat-file', 'blob', 'branch_K:file').stdout,
       'K'
     )
 
+  def testSquashBranchEmpty(self):
+    self.repo.git('checkout', 'branch_K')
+    self.repo.git('checkout', 'branch_G', '.')
+    self.repo.git('commit', '-m', 'revert all changes no branch')
+    # Should return False since the quash would result in an empty commit
+    stdout = self.repo.capture_stdio(self.gc.squash_current_branch)[0]
+    self.assertEquals(stdout, 'Nothing to commit; squashed branch is empty\n')
+
   def testRebase(self):
     self.assertSchema("""
     A B C D E F G
       B H I J K
             J L
 
     X Y Z
 
     CAT DOG
     """)
@@ skipping 112 matching lines @@
 
       self.assertEquals(self.repo.git('status', '--porcelain').stdout, STATUS_1)
 
     self.repo.run(inner)
 
 
 if __name__ == '__main__':
   sys.exit(coverage_utils.covered_main(
     os.path.join(DEPOT_TOOLS_ROOT, 'git_common.py')
   ))