Introduce and use SshCommand class for running commands via ssh

Most of the ssh parameters are given by a URL, which should be
configurable.  Additional options can be set by keyword arguments.

runcmd already has a function like this, but it doesn't take a URL and
runcmd.shell_quote doesn't handle empty strings correctly.

Use this in the Gerrit host connector.  It could be used in the Gitano
host connector as well, but I want to avoid making further changes
there that I can't test.

2 files changed, 47 insertions, 21 deletions

diff --git a/lorrycontroller/gerrit.py b/lorrycontroller/gerrit.py
index c18f2ed..dad964f 100644
--- a/lorrycontroller/gerrit.py
+++ b/lorrycontroller/gerrit.py
@@ -32,27 +32,15 @@ class GerritDownstream(hosts.DownstreamHost):
     '''
 
     def __init__(self, app_settings):
-        # XXX These need to be configurable
-        host = 'localhost'
-        port = 29418
-        user = 'lorry'
-
-        self._ssh_command_args = [
-            'ssh', '-oStrictHostKeyChecking=no', '-oBatchMode=yes', '-p%i' % port,
-            '%s@%s' % (user, host)]
-
-    def _ssh_command(self, command):
-        quoted_args = [cliapp.shell_quote(x) for x in command]
-        out = cliapp.runcmd(self._ssh_command_args + quoted_args)
-        if isinstance(out, bytes):
-            out = out.decode('utf-8', errors='replace')
-        return out
+        # XXX This needs to be configurable
+        url = 'ssh://lorry@localhost:29418'
+        self._ssh_command = hosts.SshCommand(url, StrictHostKeyChecking='no')
 
     def _has_project(self, name):
         # There's no 'does this project exist' command in Gerrit 2.9.4; 'list
         # all projects with this prefix' is as close we can get.
 
-        output = self._ssh_command([
+        output = self._ssh_command.run([
             'gerrit', 'ls-projects', '--type=ALL', '--prefix=%s' % name])
         projects = output.strip().split('\n')
 
@@ -72,17 +60,17 @@ class GerritDownstream(hosts.DownstreamHost):
             logging.info('Project %s exists in local Gerrit already.',
                          name)
         else:
-            self._ssh_command(['gerrit', 'create-project', name])
+            self._ssh_command.run(['gerrit', 'create-project', name])
             logging.info('Created %s project in local Gerrit.', name)
 
         # We can only set this metadata if we're the owner of the
         # repository.  For now, ignore failures.
         try:
             if 'head' in metadata:
-                self._ssh_command(['gerrit', 'set-head', name,
-                                   '--new-head', metadata['head']])
+                self._ssh_command.run(['gerrit', 'set-head', name,
+                                       '--new-head', metadata['head']])
             if 'description' in metadata:
-                self._ssh_command(['gerrit', 'set-project', name,
-                                   '-d', metadata['description']])
+                self._ssh_command.run(['gerrit', 'set-project', name,
+                                       '-d', metadata['description']])
         except cliapp.AppException:
             pass
diff --git a/lorrycontroller/hosts.py b/lorrycontroller/hosts.py
index 39cae57..fb892dc 100644
--- a/lorrycontroller/hosts.py
+++ b/lorrycontroller/hosts.py
@@ -14,6 +14,10 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 import abc
+import shlex
+import urllib.parse
+
+import cliapp
 
 
 class DownstreamHost(abc.ABC):
@@ -119,3 +123,37 @@ class UpstreamHost(abc.ABC):
         DownstreamHost.prepare_repo.
         '''
         pass
+
+
+class SshCommand:
+    def __init__(self, urlstring, **options):
+        try:
+            url = urllib.parse.urlsplit(urlstring, allow_fragments=False)
+            url.port
+        except ValueError:
+            raise cliapp.AppException('Invalid URL: %s' % urlstring)
+
+        if url.scheme != 'ssh':
+            raise cliapp.AppException('Not an SSH URL: %s' % urlstring)
+        if url.path not in ['', '/']:
+            raise cliapp.AppException('Unexpected path part in SSH URL')
+        if url.query != '':
+            raise cliapp.AppException('Unexpected query part in SSH URL')
+        if url.password is not None:
+            raise cliapp.AppException('Unexpected password in SSH URL')
+
+        self._ssh_args = ['ssh', '-oBatchMode=yes']
+        for key, value in options.items():
+            self._ssh_args.append('-o%s=%s' % (key, value))
+        if url.username is not None:
+            self._ssh_args.append('-oUser=%s' % url.username)
+        if url.port is not None:
+            self._ssh_args.append('-p%i' % url.port)
+        self._ssh_args.append(url.hostname)
+
+    def run(self, args):
+        quoted_args = [shlex.quote(arg) for arg in args]
+        stdout = cliapp.runcmd(self._ssh_args + quoted_args)
+        if isinstance(stdout, bytes):
+            stdout = stdout.decode('utf-8', errors='replace')
+        return stdout