bisect-kit: add switch script builds by cq builder

TEST=./switch_cros_localbuild_internal.py --bucket bisect --nodeploy --build_revlist R81-12747.0.0-25156~R81-12747.0.0-25157/1
TEST=./switch_cros_localbuild_internal.py --board coral --buildbucket_id 8894318060265125680
TEST=./switch_cros_localbuild_internal.py --build_revlist R81-12747.0.0-25156~R81-12747.0.0-25157/1
BUG=b:140721312

Change-Id: Iebac7bf293db5379000dcdde08c3ce778ea8859c
diff --git a/bisect_kit/git_util.py b/bisect_kit/git_util.py
index 21a2031..eefad2f 100644
--- a/bisect_kit/git_util.py
+++ b/bisect_kit/git_util.py
@@ -470,7 +470,7 @@
 
 
 def get_history(git_repo,
-                path,
+                path=None,
                 branch=None,
                 after=None,
                 before=None,
@@ -512,10 +512,11 @@
   if branch:
     assert not is_git_rev(branch)
     cmd += [branch]
-  # '--' is necessary otherwise if `path` is removed in current revision, git
-  # will complain it's an ambiguous argument which may be path or something
-  # else (like git branch name, tag name, etc.)
-  cmd += ['--', path]
+  if path:
+    # '--' is necessary otherwise if `path` is removed in current revision, git
+    # will complain it's an ambiguous argument which may be path or something
+    # else (like git branch name, tag name, etc.)
+    cmd += ['--', path]
 
   result = []
   for line in util.check_output(*cmd, cwd=git_repo).splitlines():