Use hash for ControlPath instead of full variables

The generated socket path can be too long, if your FQDN is very long...

Typical error message from ssh client:
unix_listener: path "/tmp/ssh-fqduawon/master-USER@HOST:PORT.qfCZ51OAZgTzVLbg" too long for Unix domain socket

Use a hashed version instead, to keep within the socket file path limit.

This requires OpenSSH_6.7p1, or later.

Change-Id: Ia4bb9ae8aac6c4ee31d5a458f917f3753f40001b
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/255632
Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Anders Björklund <anders.bjorklund.2@volvocars.com>

tests/test_git_command.py

@@ -30,6 +30,33 @@ import git_command
 import wrapper
 
 
+class SSHUnitTest(unittest.TestCase):
+  """Tests the ssh functions."""
+
+  def test_ssh_version(self):
+    """Check ssh_version() handling."""
+    ver = git_command._parse_ssh_version('Unknown\n')
+    self.assertEqual(ver, ())
+    ver = git_command._parse_ssh_version('OpenSSH_1.0\n')
+    self.assertEqual(ver, (1, 0))
+    ver = git_command._parse_ssh_version('OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.13, OpenSSL 1.0.1f 6 Jan 2014\n')
+    self.assertEqual(ver, (6, 6, 1))
+    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_sock(self):
+    """Check ssh_sock() function."""
+    with mock.patch('tempfile.mkdtemp', return_value='/tmp/foo'):
+      # old ssh version uses port
+      with mock.patch('git_command.ssh_version', return_value=(6, 6)):
+        self.assertTrue(git_command.ssh_sock().endswith('%p'))
+      git_command._ssh_sock_path = None
+      # new ssh version uses hash
+      with mock.patch('git_command.ssh_version', return_value=(6, 7)):
+        self.assertTrue(git_command.ssh_sock().endswith('%C'))
+      git_command._ssh_sock_path = None
+
+
 class GitCallUnitTest(unittest.TestCase):
   """Tests the _GitCall class (via git_command.git)."""