dedupe the --rsh options in favor of user supplied (ansible#38096)

lib/ansible/modules/files/synchronize.py

@@ -462,20 +462,30 @@ def main():
         module.fail_json(msg='either src or dest must be a localhost', rc=1)
 
     if is_rsh_needed(source, dest):
-        ssh_cmd = [module.get_bin_path('ssh', required=True), '-S', 'none']
-        if private_key is not None:
-            ssh_cmd.extend(['-i', private_key])
-        # If the user specified a port value
-        # Note:  The action plugin takes care of setting this to a port from
-        # inventory if the user didn't specify an explicit dest_port
-        if dest_port is not None:
-            ssh_cmd.extend(['-o', 'Port=%s' % dest_port])
-        if not verify_host:
-            ssh_cmd.extend(['-o', 'StrictHostKeyChecking=no', '-o', 'UserKnownHostsFile=/dev/null'])
-        ssh_cmd_str = ' '.join(shlex_quote(arg) for arg in ssh_cmd)
-        if ssh_args:
-            ssh_cmd_str += ' %s' % ssh_args
-        cmd.append('--rsh=%s' % ssh_cmd_str)
+
+        # https://github.com/ansible/ansible/issues/15907
+        has_rsh = False
+        for rsync_opt in rsync_opts:
+            if '--rsh' in rsync_opt:
+                has_rsh = True
+                break
+
+        # if the user has not supplied an --rsh option go ahead and add ours
+        if not has_rsh:
+            ssh_cmd = [module.get_bin_path('ssh', required=True), '-S', 'none']
+            if private_key is not None:
+                ssh_cmd.extend(['-i', private_key])
+            # If the user specified a port value
+            # Note:  The action plugin takes care of setting this to a port from
+            # inventory if the user didn't specify an explicit dest_port
+            if dest_port is not None:
+                ssh_cmd.extend(['-o', 'Port=%s' % dest_port])
+            if not verify_host:
+                ssh_cmd.extend(['-o', 'StrictHostKeyChecking=no', '-o', 'UserKnownHostsFile=/dev/null'])
+            ssh_cmd_str = ' '.join(shlex_quote(arg) for arg in ssh_cmd)
+            if ssh_args:
+                ssh_cmd_str += ' %s' % ssh_args
+            cmd.append('--rsh=%s' % ssh_cmd_str)
 
     if rsync_path:
         cmd.append('--rsync-path=%s' % rsync_path)