Add the SshAutoTransport transport plugin

This is an alternative to the `SshFabricTransport` that does not depend
on the `fabric` library but instead simply modifies the `SshTransport`
plugin to not require specifying any connection arguments, but that are
instead automatically parsed from the SSH config. The `fabric` plugin
anyway uses `paramiko` under the hood to perform the actual connections,
just as the `SshTransport` plugin, and the logic to automatically
determine connection parameters is not that complicated for default
input arguments to the `fabric.Connection` class. It does do some clever
stuff with proxy commands and jumps, but that is also already
implemented by `SshTransport`. So there is little reason to add another
dependency.

pyproject.toml

@@ -175,6 +175,7 @@ requires-python = '>=3.9'
 [project.entry-points.'aiida.transports']
 'core.local' = 'aiida.transports.plugins.local:LocalTransport'
 'core.ssh' = 'aiida.transports.plugins.ssh:SshTransport'
+'core.ssh_auto' = 'aiida.transports.plugins.ssh_auto:SshAutoTransport'
 'core.ssh_fabric' = 'aiida.transports.plugins.ssh_fabric:SshFabricTransport'
 
 [project.entry-points.'aiida.workflows']

src/aiida/transports/plugins/ssh_auto.py

@@ -0,0 +1,50 @@
+###########################################################################
+# Copyright (c), The AiiDA team. All rights reserved.                     #
+# This file is part of the AiiDA code.                                    #
+#                                                                         #
+# The code is hosted on GitHub at https://github.com/aiidateam/aiida-core #
+# For further information on the license, see the LICENSE.txt file        #
+# For further information please visit http://www.aiida.net               #
+###########################################################################
+"""Plugin for transport over SSH (and SFTP for file transfer)."""
+
+import pathlib
+
+import paramiko
+
+from .ssh import SshTransport
+
+__all__ = ('SshAutoTransport',)
+
+
+class SshAutoTransport(SshTransport):
+    """Support connection, command execution and data transfer to remote computers via SSH+SFTP."""
+
+    _valid_connect_params = []
+    _valid_auth_options = []
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs, key_policy='AutoAddPolicy')
+
+        config_ssh = paramiko.SSHConfig()
+
+        with (pathlib.Path('~').expanduser() / '.ssh' / 'config').open() as handle:
+            config_ssh.parse(handle)
+
+        if self._machine not in config_ssh.get_hostnames():
+            self.logger.warning(
+                f'The host `{self._machine}` is not defined in SSH config, connection will most likely fail to open.'
+            )
+
+        config_host = config_ssh.lookup(self._machine)
+
+        self._connect_args = {
+            'port': config_host.get('port', 22),
+            'username': config_host.get('user'),
+            'key_filename': config_host.get('identityfile', []),
+            'timeout': config_host.get('connecttimeout', 60),
+            'proxy_command': config_host.get('proxycommand', None),
+            'proxy_jump': config_host.get('proxyjump', None),
+        }
+
+        self._machine = config_host['hostname']