deprecate 'smart' connection value (#81218)

Co-authored-by: Jordan Borean <jborean93@gmail.com>

changelogs/fragments/smart_connection_bye.yml

@@ -0,0 +1,4 @@
+minor_changes:
+  - DEFAULT_TRANSPORT now defaults to 'ssh', the old 'smart' option is being deprecated as versions of OpenSSH without control persist are basically not present anymore.
+deprecated_features:
+  - the 'smart' option for setting a connection plugin is being removed as it's main purpose (choosing between ssh and paramiko) is now irrelevant.

lib/ansible/config/base.yml

@@ -1102,10 +1102,11 @@ DEFAULT_TIMEOUT:
   - {key: timeout, section: defaults}
   type: integer
 DEFAULT_TRANSPORT:
-  # note that ssh_utils refs this and needs to be updated if removed
   name: Connection plugin
-  default: smart
-  description: "Default connection plugin to use, the 'smart' option will toggle between 'ssh' and 'paramiko' depending on controller OS and ssh versions"
+  default: ssh
+  description:
+    - Can be any connection plugin available to your ansible installation.
+    - There is also a (DEPRECATED) special 'smart' option, that will toggle between 'ssh' and 'paramiko' depending on controller OS and ssh versions.
   env: [{name: ANSIBLE_TRANSPORT}]
   ini:
   - {key: transport, section: defaults}

lib/ansible/utils/ssh_functions.py

@@ -25,6 +25,9 @@ import subprocess
 from ansible import constants as C
 from ansible.module_utils.common.text.converters import to_bytes
 from ansible.module_utils.compat.paramiko import paramiko
+from ansible.utils.display import Display
+
+display = Display()
 
 
 _HAS_CONTROLPERSIST = {}  # type: dict[str, bool]
@@ -51,13 +54,11 @@ def check_for_controlpersist(ssh_executable):
     return has_cp
 
 
-# TODO: move to 'smart' connection plugin that subclasses to ssh/paramiko as needed.
 def set_default_transport():
 
     # deal with 'smart' connection .. one time ..
     if C.DEFAULT_TRANSPORT == 'smart':
-        # TODO: check if we can deprecate this as ssh w/o control persist should
-        # not be as common anymore.
+        display.deprecated("The 'smart' option for connections is deprecated. Set the connection plugin directly instead.", version=2.19)
 
         # see if SSH can support ControlPersist if not use paramiko
         if not check_for_controlpersist('ssh') and paramiko is not None: