diff --git a/pre-upload.py b/pre-upload.py
index f2938d5..27059b4 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -113,6 +113,21 @@
 # General Helpers
 
 
+class Cache(object):
+  """General helper for caching git content."""
+
+  def __init__(self):
+    self._cache = {}
+
+  def get_subcache(self, scope):
+    return self._cache.setdefault(scope, {})
+
+  def clear(self):
+    self._cache.clear()
+
+CACHE = Cache()
+
+
 Project = collections.namedtuple('Project', ['name', 'dir', 'remote'])
 
 
@@ -248,19 +263,32 @@
   a full file, you should check that first.  One way to detect is that the
   content will not have any newlines.
   """
+  # Make sure people don't accidentally pass in full paths which will never
+  # work.  You need to use relative=True with _get_affected_files.
+  if path.startswith('/'):
+    raise ValueError('_get_file_content must be called with relative paths: %s'
+                     % (path,))
+
+  # {<commit>: {<path1>: <content>, <path2>: <content>}}
+  cache = CACHE.get_subcache('get_file_content')
+  if path in cache:
+    return cache[path]
+
   if commit == PRE_SUBMIT:
-    return _run_command(['git', 'diff', 'HEAD', path])
+    content = _run_command(['git', 'diff', 'HEAD', path])
   else:
-    # Make sure people don't accidentally pass in full paths which will never
-    # work.  You need to use relative=True with _get_affected_files.
-    if path.startswith('/'):
-      raise ValueError('_get_file_content must be called with relative paths: '
-                       + path)
-    return _run_command(['git', 'show', '%s:%s' % (commit, path)])
+    content = _run_command(['git', 'show', '%s:%s' % (commit, path)])
+  cache[path] = content
+  return content
 
 
 def _get_file_diff(path, commit):
   """Returns a list of (linenum, lines) tuples that the commit touched."""
+  # {<commit>: {<path1>: <content>, <path2>: <content>}}
+  cache = CACHE.get_subcache('get_file_diff')
+  if path in cache:
+    return cache[path]
+
   if commit == PRE_SUBMIT:
     command = ['git', 'diff', '-p', '--pretty=format:', '--no-ext-diff', 'HEAD',
                path]
@@ -280,6 +308,7 @@
       new_lines.append((line_num, _try_utf8_decode(line[1:])))
     if not line.startswith('-'):
       line_num += 1
+  cache[path] = new_lines
   return new_lines
 
 
@@ -370,7 +399,11 @@
                          '--name-only', 'HEAD']).split()
 
   path = os.getcwd()
-  files = git.RawDiff(path, '%s^!' % commit)
+  # {<commit>: {<path1>: <content>, <path2>: <content>}}
+  cache = CACHE.get_subcache('get_affected_files')
+  if path not in cache:
+    cache[path] = git.RawDiff(path, '%s^!' % commit)
+  files = cache[path]
 
   # Filter out symlinks.
   if not include_symlinks:
@@ -410,7 +443,13 @@
   """Returns the full commit message of a commit."""
   if commit == PRE_SUBMIT:
     return ''
-  return _run_command(['git', 'log', '--format=%s%n%n%b', commit + '^!'])
+
+  # {<commit>: <content>}
+  cache = CACHE.get_subcache('get_commit_desc')
+  if commit not in cache:
+    cache[commit] = _run_command(['git', 'log', '--format=%s%n%n%b',
+                                  commit + '^!'])
+  return cache[commit]
 
 
 def _check_lines_in_diff(commit, files, check_callable, error_description):
@@ -1939,6 +1978,8 @@
   commit_count = len(commit_list)
   hook_count = len(hooks)
   for i, commit in enumerate(commit_list):
+    CACHE.clear()
+
     error_list = []
     for h, hook in enumerate(hooks):
       output = ('PRESUBMIT.cfg: [%i/%i]: %s: Running [%i/%i] %s' %
diff --git a/pre-upload_unittest.py b/pre-upload_unittest.py
index 88d665b..da27cba 100755
--- a/pre-upload_unittest.py
+++ b/pre-upload_unittest.py
@@ -38,7 +38,14 @@
   return pre_upload.Project(project_name, None, None)
 
 
-class TryUTF8DecodeTest(cros_test_lib.TestCase):
+class PreUploadTestCase(cros_test_lib.MockTestCase):
+  """Common test case base."""
+
+  def setUp(self):
+    pre_upload.CACHE.clear()
+
+
+class TryUTF8DecodeTest(PreUploadTestCase):
   """Verify we sanely handle unicode content."""
 
   def runTest(self):
@@ -51,7 +58,7 @@
     self.assertEquals('\x80', pre_upload._try_utf8_decode('\x80'))
 
 
-class CheckNoLongLinesTest(cros_test_lib.MockTestCase):
+class CheckNoLongLinesTest(PreUploadTestCase):
   """Tests for _check_no_long_lines."""
 
   def setUp(self):
@@ -130,8 +137,9 @@
         ProjectNamed('PROJECT'), 'COMMIT', options=['--exclude_regex=foo']))
 
 
-class CheckTabbedIndentsTest(cros_test_lib.MockTestCase):
+class CheckTabbedIndentsTest(PreUploadTestCase):
   """Tests for _check_tabbed_indents."""
+
   def setUp(self):
     self.PatchObject(pre_upload,
                      '_get_affected_files',
@@ -167,7 +175,7 @@
                       failure.items)
 
 
-class CheckProjectPrefix(cros_test_lib.MockTempDirTestCase):
+class CheckProjectPrefix(PreUploadTestCase, cros_test_lib.TempDirTestCase):
   """Tests for _check_project_prefix."""
 
   def setUp(self):
@@ -222,7 +230,7 @@
         pre_upload._check_project_prefix(ProjectNamed('PROJECT'), 'COMMIT'))
 
 
-class CheckFilePathCharTypeTest(cros_test_lib.MockTestCase):
+class CheckFilePathCharTypeTest(PreUploadTestCase):
   """Tests for _check_filepath_chartype."""
 
   def setUp(self):
@@ -262,7 +270,7 @@
                       failure.items)
 
 
-class CheckKernelConfig(cros_test_lib.MockTestCase):
+class CheckKernelConfig(PreUploadTestCase):
   """Tests for _kernel_configcheck."""
 
   def setUp(self):
@@ -295,7 +303,7 @@
     self.assertFalse(failure)
 
 
-class CheckJson(cros_test_lib.MockTestCase):
+class CheckJson(PreUploadTestCase):
   """Tests for _run_json_check."""
 
   def setUp(self):
@@ -334,7 +342,7 @@
     self.content_mock.assert_called_once_with('/data.json', 'COMMIT')
 
 
-class CheckManifests(cros_test_lib.MockTestCase):
+class CheckManifests(PreUploadTestCase):
   """Tests _check_manifests."""
 
   def setUp(self):
@@ -407,7 +415,7 @@
     self._testReject('EBUILD foo\n')
 
 
-class CheckConfigParsing(cros_test_lib.MockTestCase):
+class CheckConfigParsing(PreUploadTestCase):
   """Tests _check_cq_ini_well_formed."""
 
   def setUp(self):
@@ -447,7 +455,7 @@
     self.assertTrue(isinstance(m, pre_upload.HookFailure))
 
 
-class CheckPortageMakeUseVar(cros_test_lib.MockTestCase):
+class CheckPortageMakeUseVar(PreUploadTestCase):
   """Tests for _check_portage_make_use_var."""
 
   def setUp(self):
@@ -495,7 +503,7 @@
     self.assertFalse(failure, failure)
 
 
-class CheckEbuildEapi(cros_test_lib.MockTestCase):
+class CheckEbuildEapi(PreUploadTestCase):
   """Tests for _check_ebuild_eapi."""
 
   PORTAGE_STABLE = ProjectNamed('chromiumos/overlays/portage-stable')
@@ -595,7 +603,7 @@
     self.assertEqual(ret, None)
 
 
-class CheckEbuildKeywords(cros_test_lib.MockTestCase):
+class CheckEbuildKeywords(PreUploadTestCase):
   """Tests for _check_ebuild_keywords."""
 
   def setUp(self):
@@ -664,7 +672,7 @@
     self._CheckContent('# HEADER\nKEYWORDS="~arm x86"\nblah\n', True)
 
 
-class CheckEbuildVirtualPv(cros_test_lib.MockTestCase):
+class CheckEbuildVirtualPv(PreUploadTestCase):
   """Tests for _check_ebuild_virtual_pv."""
 
   PORTAGE_STABLE = ProjectNamed('chromiumos/overlays/portage-stable')
@@ -745,7 +753,7 @@
     ret = pre_upload._check_ebuild_virtual_pv(self.PRIVATE_VARIANT_OVERLAY, 'H')
     self.assertEqual(ret, None)
 
-class CheckCrosLicenseCopyrightHeader(cros_test_lib.MockTestCase):
+class CheckCrosLicenseCopyrightHeader(PreUploadTestCase):
   """Tests for _check_cros_license."""
 
   def setUp(self):
@@ -847,7 +855,7 @@
     self.content_mock.return_value = ('owner@chromium.org')
     self.assertFalse(pre_upload._check_cros_license('proj', 'sha1'))
 
-class CheckAOSPLicenseCopyrightHeader(cros_test_lib.MockTestCase):
+class CheckAOSPLicenseCopyrightHeader(PreUploadTestCase):
   """Tests for _check_aosp_license."""
 
   def setUp(self):
@@ -930,7 +938,7 @@
     self.content_mock.return_value = ('owner@chromium.org')
     self.assertEqual(None, pre_upload._check_aosp_license('proj', 'sha1'))
 
-class CheckLayoutConfTestCase(cros_test_lib.MockTestCase):
+class CheckLayoutConfTestCase(PreUploadTestCase):
   """Tests for _check_layout_conf."""
 
   def setUp(self):
@@ -1017,7 +1025,7 @@
     self.assertRejected(['metadata/layout.conf'])
 
 
-class CommitMessageTestCase(cros_test_lib.MockTestCase):
+class CommitMessageTestCase(PreUploadTestCase):
   """Test case for funcs that check commit messages."""
 
   def setUp(self):
@@ -1333,7 +1341,7 @@
                           src_file=src_file, dst_file=dst_file)
 
 
-class HelpersTest(cros_test_lib.MockTempDirTestCase):
+class HelpersTest(PreUploadTestCase, cros_test_lib.TempDirTestCase):
   """Various tests for utility functions."""
 
   def setUp(self):
@@ -1433,7 +1441,7 @@
     self.assertEquals(pre_upload._get_affected_files('HEAD', relative=True), [])
 
 
-class ExecFilesTest(cros_test_lib.MockTestCase):
+class ExecFilesTest(PreUploadTestCase):
   """Tests for _check_exec_files."""
 
   def setUp(self):
@@ -1476,7 +1484,7 @@
     self.assertEqual(pre_upload._check_exec_files('proj', 'commit'), None)
 
 
-class CheckForUprev(cros_test_lib.MockTempDirTestCase):
+class CheckForUprev(PreUploadTestCase, cros_test_lib.TempDirTestCase):
   """Tests for _check_for_uprev."""
 
   def setUp(self):
@@ -1563,7 +1571,7 @@
     self.assertAccepted([DiffEntry(src_file='c/p/files/f', status='M')])
 
 
-class DirectMainTest(cros_test_lib.MockTempDirTestCase):
+class DirectMainTest(PreUploadTestCase, cros_test_lib.TempDirTestCase):
   """Tests for direct_main()"""
 
   def setUp(self):
@@ -1623,7 +1631,7 @@
         mock.ANY, proj_dir=mock.ANY, commit_list=commits, presubmit=mock.ANY)
 
 
-class CheckRustfmtTest(cros_test_lib.MockTestCase):
+class CheckRustfmtTest(PreUploadTestCase):
   """Tests for _check_rustfmt."""
 
   def setUp(self):