Merge branch 'cd-dot-command'

* cd-dot-command:
  Update README with docs for .cd command
  Add tests for .cd dot command
  Proof of concept for .cd command

Conflicts:
	awsshell/app.py
	tests/unit/test_app.py

Closes #94.

README.rst

@@ -261,6 +261,19 @@ will be printed.
     Current shell profile: demo
 
 
+.cd
+~~~
+
+You can change the current working directory of the aws-shell by using
+the ``.cd`` command::
+
+    aws> !pwd
+    /usr
+    aws> .cd /tmp
+    aws> !pwd
+    /tmp
+
+
 Executing Shell Commands
 ------------------------
 

awsshell/app.py

@@ -45,6 +45,24 @@ class InputInterrupt(Exception):
     pass
 
 
+class ChangeDirHandler(object):
+    def __init__(self, output=sys.stdout, err=sys.stderr, chdir=os.chdir):
+        self._output = output
+        self._err = err
+        self._chdir = chdir
+
+    def run(self, command, application):
+        # command is a list of parsed commands
+        if len(command) != 2:
+            self._err.write("invalid syntax, must be: .cd dirname\n")
+            return
+        dirname = os.path.expandvars(os.path.expanduser(command[1]))
+        try:
+            self._chdir(dirname)
+        except OSError as e:
+            self._err.write("cd: %s\n" % e)
+
+
 class EditHandler(object):
     def __init__(self, popen_cls=None, env=None):
         if popen_cls is None:
@@ -121,6 +139,7 @@ class DotCommandHandler(object):
     HANDLER_CLASSES = {
         'edit': EditHandler,
         'profile': ProfileHandler,
+        'cd': ChangeDirHandler,
     }
 
     def __init__(self, output=sys.stdout, err=sys.stderr):

tests/unit/test_app.py

@@ -93,3 +93,26 @@ def test_delegates_to_complete_changing_profile():
     shell.profile = 'mynewprofile'
     assert completer.change_profile.call_args == mock.call('mynewprofile')
     assert shell.profile == 'mynewprofile'
+
+
+def test_cd_handler_can_chdir():
+    chdir = mock.Mock()
+    handler = app.ChangeDirHandler(chdir=chdir)
+    handler.run(['.cd', 'foo/bar'], None)
+    assert chdir.call_args == mock.call('foo/bar')
+
+
+def test_chdir_syntax_error_prints_err_msg(errstream):
+    chdir = mock.Mock()
+    handler = app.ChangeDirHandler(err=errstream, chdir=chdir)
+    handler.run(['.cd'], None)
+    assert 'invalid syntax' in errstream.getvalue()
+    assert not chdir.called
+
+
+def test_error_displayed_when_chdir_fails(errstream):
+    chdir = mock.Mock()
+    chdir.side_effect = OSError("FAILED")
+    handler = app.ChangeDirHandler(err=errstream, chdir=chdir)
+    handler.run(['.cd', 'foo'], None)
+    assert 'FAILED' in errstream.getvalue()