git_command: switch version caches to functools

Simplifies the code a bit to use the stdlib cache helper.

Change-Id: I778e90100ce748a71cc3a5a5d67dda403334315e
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/305482
Reviewed-by: Raman Tenneti <rtenneti@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

git_command.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import functools
 import os
 import re
 import sys
@@ -45,7 +46,6 @@ LAST_CWD = None
 _ssh_proxy_path = None
 _ssh_sock_path = None
 _ssh_clients = []
-_ssh_version = None
 
 
 def _run_ssh_version():
@@ -64,16 +64,14 @@ def _parse_ssh_version(ver_str=None):
     return ()
 
 
+@functools.lru_cache(maxsize=None)
 def ssh_version():
   """return ssh version as a tuple"""
-  global _ssh_version
-  if _ssh_version is None:
   try:
-      _ssh_version = _parse_ssh_version()
+    return _parse_ssh_version()
   except subprocess.CalledProcessError:
     print('fatal: unable to detect ssh version', file=sys.stderr)
     sys.exit(1)
-  return _ssh_version
 
 
 def ssh_sock(create=True):
@@ -125,18 +123,14 @@ def terminate_ssh_clients():
   _ssh_clients = []
 
 
-_git_version = None
-
-
 class _GitCall(object):
+  @functools.lru_cache(maxsize=None)
   def version_tuple(self):
-    global _git_version
-    if _git_version is None:
-      _git_version = Wrapper().ParseGitVersion()
-      if _git_version is None:
+    ret = Wrapper().ParseGitVersion()
+    if ret is None:
       print('fatal: unable to detect git version', file=sys.stderr)
       sys.exit(1)
-    return _git_version
+    return ret
 
   def __getattr__(self, name):
     name = name.replace('_', '-')

tests/test_git_command.py

@@ -29,8 +29,8 @@ import wrapper
 class SSHUnitTest(unittest.TestCase):
   """Tests the ssh functions."""
 
-  def test_ssh_version(self):
-    """Check ssh_version() handling."""
+  def test_parse_ssh_version(self):
+    """Check parse_ssh_version() handling."""
     ver = git_command._parse_ssh_version('Unknown\n')
     self.assertEqual(ver, ())
     ver = git_command._parse_ssh_version('OpenSSH_1.0\n')
@@ -40,6 +40,11 @@ class SSHUnitTest(unittest.TestCase):
     ver = git_command._parse_ssh_version('OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n  7 Dec 2017\n')
     self.assertEqual(ver, (7, 6))
 
+  def test_ssh_version(self):
+    """Check ssh_version() handling."""
+    with mock.patch('git_command._run_ssh_version', return_value='OpenSSH_1.2\n'):
+      self.assertEqual(git_command.ssh_version(), (1, 2))
+
   def test_ssh_sock(self):
     """Check ssh_sock() function."""
     with mock.patch('tempfile.mkdtemp', return_value='/tmp/foo'):