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

tests/git_common_test.py

Index: tests/git_common_test.py
diff --git a/tests/git_common_test.py b/tests/git_common_test.py
index ee44eb390f87a0c1d05d4bd5709e819772961036..029c823c14d3bf4857cbaa0ba3c2e445fc29d5aa 100755
--- a/tests/git_common_test.py
+++ b/tests/git_common_test.py
@@ -561,10 +561,17 @@ class GitMutableStructuredTest(git_test_utils.GitRepoReadWriteTestBase,
       ('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':
@@ -580,6 +587,14 @@ class GitMutableStructuredTest(git_test_utils.GitRepoReadWriteTestBase,
       '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