Avoid repeat _bash_command and gotocomputer_command

`bash_command` are used in three places and set by `use_login_shell`.
Encapsulate it as attribute `_bash_command_str` of `Transport`.

gotocompyter_command have same string for local and ssh transport
plugin, Encapsulate the string as `_gotocomputer_string` in `Transport`
class.

aiida/transports/plugins/local.py

@@ -743,10 +743,7 @@ def _exec_command_internal(self, command, **kwargs):  # pylint: disable=unused-a
 
         # Note: The outer shell will eat one level of escaping, while
         # 'bash -l -c ...' will eat another. Thus, we need to escape again.
-        if self._use_login_shell:
-            bash_commmand = 'bash -l -c '
-        else:
-            bash_commmand = 'bash -c '
+        bash_commmand = self._bash_command_str + '-c '
 
         command = bash_commmand + escape_for_bash(command)
 
@@ -807,11 +804,8 @@ def gotocomputer_command(self, remotedir):
 
         :param str remotedir: the full path of the remote directory
         """
-        script = ' ; '.join([
-            'if [ -d {escaped_remotedir} ]', 'then cd {escaped_remotedir}', 'bash', "else echo ' ** The directory'",
-            "echo ' ** {remotedir}'", "echo ' ** seems to have been deleted, I logout...'", 'fi'
-        ]).format(escaped_remotedir="'{}'".format(remotedir), remotedir=remotedir)
-        cmd = 'bash -c "{}"'.format(script)
+        connect_string = self._gotocomputer_string(remotedir)
+        cmd = 'bash -c {}'.format(connect_string)
         return cmd
 
     def rename(self, oldpath, newpath):

aiida/transports/plugins/ssh.py

@@ -310,13 +310,6 @@ def _get_compress_suggestion_string(cls, computer):  # pylint: disable=unused-ar
         """
         return 'True'
 
-    @classmethod
-    def _get_use_login_shell_suggestion_string(cls, computer):  # pylint: disable=unused-argument
-        """
-        Return a suggestion for the specific field.
-        """
-        return 'True'
-
     @classmethod
     def _get_load_system_host_keys_suggestion_string(cls, computer):  # pylint: disable=unused-argument
         """
@@ -368,8 +361,6 @@ def __init__(self, *args, **kwargs):
         Initialize the SshTransport class.
 
         :param machine: the machine to connect to
-        :param use_login_shell: (optional, default True)
-           if False, do not use a login shell when executing command
         :param load_system_host_keys: (optional, default False)
            if False, do not load the system host keys
         :param key_policy: (optional, default = paramiko.RejectPolicy())
@@ -1241,10 +1232,7 @@ def _exec_command_internal(self, command, combine_stderr=False, bufsize=-1):  #
 
         # Note: The default shell will eat one level of escaping, while
         # 'bash -l -c ...' will eat another. Thus, we need to escape again.
-        if self._use_login_shell:
-            bash_commmand = 'bash -l -c '
-        else:
-            bash_commmand = 'bash -c '
+        bash_commmand = self._bash_command_str + '-c '
 
         channel.exec_command(bash_commmand + escape_for_bash(command_to_execute))
 
@@ -1312,21 +1300,14 @@ def gotocomputer_command(self, remotedir):
             further_params.append('-i {}'.format(escape_for_bash(self._connect_args['key_filename'])))
 
         further_params_str = ' '.join(further_params)
-        # I use triple strings because I both have single and double quotes, but I still want everything in
-        # a single line
-        connect_string = (
-            """ssh -t {machine} {further_params} "if [ -d {escaped_remotedir} ] ;"""
-            """ then cd {escaped_remotedir} ; bash -l ; else echo '  ** The directory' ; """
-            """echo '  ** {remotedir}' ; echo '  ** seems to have been deleted, I logout...' ; fi" """.format(
-                further_params=further_params_str,
-                machine=self._machine,
-                escaped_remotedir="'{}'".format(remotedir),
-                remotedir=remotedir
-            )
-        )
 
-        # print connect_string
-        return connect_string
+        connect_string = self._gotocomputer_string(remotedir)
+        cmd = 'ssh -t {machine} {further_params} {connect_string}'.format(
+            further_params=further_params_str,
+            machine=self._machine,
+            connect_string=connect_string,
+        )
+        return cmd
 
     def symlink(self, remotesource, remotedestination):
         """

aiida/transports/transport.py

@@ -77,10 +77,20 @@ class Transport(abc.ABC):
     def __init__(self, *args, **kwargs):  # pylint: disable=unused-argument
         """
         __init__ method of the Transport base class.
+
+        :param safe_interval: (optional, default self._DEFAULT_SAFE_OPEN_INTERVAL)
+           Minimum time interval in seconds between opening new connections.
+        :param use_login_shell: (optional, default True)
+           if False, do not use a login shell when executing command
         """
         from aiida.common import AIIDA_LOGGER
         self._safe_open_interval = kwargs.pop('safe_interval', self._DEFAULT_SAFE_OPEN_INTERVAL)
         self._use_login_shell = kwargs.pop('use_login_shell', True)
+        if self._use_login_shell:
+            self._bash_command_str = 'bash -l '
+        else:
+            self._bash_command_str = 'bash '
+
         self._logger = AIIDA_LOGGER.getChild('transport').getChild(self.__class__.__name__)
         self._logger_extra = None
         self._is_open = False
@@ -212,6 +222,13 @@ def _get_safe_interval_suggestion_string(cls, computer):  # pylint: disable=unus
         """
         return cls._DEFAULT_SAFE_OPEN_INTERVAL
 
+    @classmethod
+    def _get_use_login_shell_suggestion_string(cls, computer):  # pylint: disable=unused-argument
+        """
+        Return a suggestion for the specific field.
+        """
+        return 'True'
+
     @property
     def logger(self):
         """
@@ -775,6 +792,18 @@ def glob0(self, dirname, basename):
     def has_magic(self, string):
         return self._MAGIC_CHECK.search(string) is not None
 
+    def _gotocomputer_string(self, remotedir):
+        """command executed when goto computer."""
+        connect_string = (
+            """ "if [ -d {escaped_remotedir} ] ;"""
+            """ then cd {escaped_remotedir} ; {bash_command} ; else echo '  ** The directory' ; """
+            """echo '  ** {remotedir}' ; echo '  ** seems to have been deleted, I logout...' ; fi" """.format(
+                bash_command=self._bash_command_str, escaped_remotedir="'{}'".format(remotedir), remotedir=remotedir
+            )
+        )
+
+        return connect_string
+
 
 class TransportInternalError(InternalError):
     """

tests/transports/test_local.py

@@ -48,3 +48,16 @@ def test_basic():
         """Test constructor."""
         with LocalTransport():
             pass
+
+
+def test_gotocomputer():
+    """Test gotocomputer"""
+    with LocalTransport() as transport:
+        cmd_str = transport.gotocomputer_command('/remote_dir/')
+
+        expected_str = (
+            """bash -c  "if [ -d '/remote_dir/' ] ;"""
+            """ then cd '/remote_dir/' ; bash -l  ; else echo '  ** The directory' ; """
+            """echo '  ** /remote_dir/' ; echo '  ** seems to have been deleted, I logout...' ; fi" """
+        )
+        assert cmd_str == expected_str

tests/transports/test_ssh.py

@@ -55,3 +55,16 @@ def test_no_host_key(self):
 
         # Reset logging level
         logging.disable(logging.NOTSET)
+
+
+def test_gotocomputer():
+    """Test gotocomputer"""
+    with SshTransport(machine='localhost', timeout=30, use_login_shell=False, key_policy='AutoAddPolicy') as transport:
+        cmd_str = transport.gotocomputer_command('/remote_dir/')
+
+        expected_str = (
+            """ssh -t localhost   "if [ -d '/remote_dir/' ] ;"""
+            """ then cd '/remote_dir/' ; bash  ; else echo '  ** The directory' ; """
+            """echo '  ** /remote_dir/' ; echo '  ** seems to have been deleted, I logout...' ; fi" """
+        )
+        assert cmd_str == expected_str