Run "git stash" and "git stash apply" before and after a dry test run.

tools/auto_bisect/bisect_perf_regression_test.py

Index: tools/auto_bisect/bisect_perf_regression_test.py
diff --git a/tools/auto_bisect/bisect_perf_regression_test.py b/tools/auto_bisect/bisect_perf_regression_test.py
index c10ed78a1fa3bc2d0ddeb75a86f66d0045476a7e..ff13cb0bb609e3c8f6d78a7275343ed6ef20b835 100644
--- a/tools/auto_bisect/bisect_perf_regression_test.py
+++ b/tools/auto_bisect/bisect_perf_regression_test.py
@@ -151,10 +151,12 @@ def _GenericDryRun(options, print_results=False):
   Returns:
     The results dictionary as returned by the bisect Run method.
   """
+  _AbortIfThereAreUncommittedChanges()
   # Disable rmtree to avoid deleting local trees.
   old_rmtree = shutil.rmtree
+  shutil.rmtree = lambda path, on_error: None
+  # git reset HEAD may be run during the dry run, which removes staged changes.
   try:
-    shutil.rmtree = lambda path, onerror: None
     bisect_instance = _GetBisectPerformanceMetricsInstance(options)
     results = bisect_instance.Run(
         bisect_instance.opts.command, bisect_instance.opts.bad_revision,
@@ -168,6 +170,15 @@ def _GenericDryRun(options, print_results=False):
     shutil.rmtree = old_rmtree
 
 
+def _AbortIfThereAreUncommittedChanges():
+  """Exits the test prematurely if there are staged changes."""
+  changes = bisect_utils.CheckRunGit(['status', '--short'])
+  if changes.strip():

[prasadv, 2015/01/27 22:32:32]

What does "CheckRunGit" returns when there is no changes? if None then
changes.strip() will fail.

[qyearsley, 2015/01/27 23:49:01]

CheckRunGit returns an empty string when there are no changes, e.g.:
('', 0)

So, this means calling strip() should be unnecessary. Changed it to not call
strip() and added a comment.

+    print 'There are un-committed changes in the current branch.'
+    print 'Aborting the tests to avoid destroying local changes.'
+    sys.exit(1)
+
+
 class BisectPerfRegressionTest(unittest.TestCase):
   """Test case for other functions and classes in bisect-perf-regression.py."""