Remove shell override in synchronize action plugin

Setting the shell from the executable basename is technically wrong,
Ansible will determine the right shell to use on its own so setting it
to None is safer

plugins/action/synchronize.py

@@ -17,8 +17,6 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
-import os.path
-
 from ansible import constants as C
 from ansible.module_utils.six import string_types
 from ansible.module_utils.six.moves import shlex_quote
@@ -301,8 +299,6 @@ class ActionModule(ActionBase):
                         break
                 if localhost_shell:
                     break
-            else:
-                localhost_shell = os.path.basename(C.DEFAULT_EXECUTABLE)
             self._play_context.shell = localhost_shell
 
             # Unlike port, there can be only one executable

tests/unit/plugins/action/fixtures/synchronize/basic/meta.yaml

@@ -11,7 +11,8 @@ hostvars:
 asserts:
   - hasattr(SAM._connection, 'ismock')
   - SAM._connection.transport == 'local'
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self.execute_called
   - self.final_module_args['_local_rsync_path'] == 'rsync'
   - self.final_module_args['src'] == '/tmp/deleteme'

tests/unit/plugins/action/fixtures/synchronize/basic_become/meta.yaml

@@ -32,7 +32,8 @@ asserts:
   - self.final_module_args['dest'] == 'root@el6host:/tmp/deleteme'
   - self.task.become == True
   - self.task.become_user == None
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self._play_context.remote_addr == 'el6host'
   - self._play_context.remote_user == 'root'
   - self._play_context.become == False

tests/unit/plugins/action/fixtures/synchronize/basic_become_cli/meta.yaml

@@ -32,7 +32,8 @@ asserts:
   - self.final_module_args['dest'] == 'root@el6host:/tmp/deleteme'
   - self.task.become == None
   - self.task.become_user == None
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self._play_context.remote_addr == 'el6host'
   - self._play_context.remote_user == 'root'
   - self._play_context.become == False

tests/unit/plugins/action/fixtures/synchronize/basic_vagrant/meta.yaml

@@ -22,7 +22,8 @@ asserts:
   - self.final_module_args['dest_port'] == 2202
   - self.final_module_args['src'] == '/tmp/deleteme'
   - self.final_module_args['dest'] == 'vagrant@127.0.0.1:/tmp/deleteme'
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self._play_context.remote_addr == '127.0.0.1'
   - self._play_context.remote_user == 'vagrant'
   - self._play_context.become == False

tests/unit/plugins/action/fixtures/synchronize/basic_vagrant_become_cli/meta.yaml

@@ -25,7 +25,8 @@ asserts:
   - self.final_module_args['dest_port'] == 2202
   - self.final_module_args['src'] == '/tmp/deleteme'
   - self.final_module_args['dest'] == 'vagrant@127.0.0.1:/tmp/deleteme'
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self._play_context.remote_addr == '127.0.0.1'
   - self._play_context.remote_user == 'vagrant'
   - self._play_context.become == False

tests/unit/plugins/action/fixtures/synchronize/basic_vagrant_sudo/meta.yaml

@@ -22,7 +22,8 @@ asserts:
   - self.final_module_args['dest_port'] == 2202
   - self.final_module_args['src'] == '/tmp/deleteme'
   - self.final_module_args['dest'] == 'vagrant@127.0.0.1:/tmp/deleteme'
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self._play_context.remote_addr == '127.0.0.1'
   - self._play_context.remote_user == 'vagrant'
   - self._play_context.become == False

tests/unit/plugins/action/fixtures/synchronize/basic_with_private_key/meta.yaml

@@ -18,7 +18,8 @@ task_args:
 asserts:
   - hasattr(SAM._connection, 'ismock')
   - SAM._connection.transport == 'local'
-  - self._play_context.shell == 'sh'
+  - self._play_context.shell == None
+  - self._play_context.executable == '/bin/sh'
   - self.execute_called
   - self.final_module_args['_local_rsync_path'] == 'rsync'
   - self.final_module_args['src'] == '/tmp/deleteme'