ssh.py: support finding sshuttle in "$HOME/.../sshuttle"

If you ran sshuttle from /home/apenwarr/sshuttle/sshuttle, we would
automatically add /home/apenwarr/sshuttle to the PATH before trying to
execute sshuttle on the remote machine.  That way, if you install it in the
same place on two computers, the client would still be able to start the
server.

Someone reported, though, that if they installed the client in
/home/apenwarr/sshuttle/shuttle, and the server in /root/sshuttle/sshuttle,
then used "-r root@servername", it wasn't able to find the program.

Similar problems would happen if you're apenwarr at home and averyp at work.

So what we now do is add *two* directories to the PATH:
/home/apenwarr/sshuttle and $HOME/sshuttle, where $HOME is the value of
$HOME on the *server*, not the client.  So it'll find it in either place.

ssh.py

@@ -1,10 +1,16 @@
 import sys, os, re, subprocess, socket
 import helpers
+from helpers import *
 
 def connect(rhost):
     main_exe = sys.argv[0]
     nicedir = os.path.split(os.path.abspath(main_exe))[0]
     nicedir = re.sub(r':', "_", nicedir)
+    myhome = os.path.expanduser('~') + '/'
+    if nicedir.startswith(myhome):
+        nicedir2 = nicedir[len(myhome):]
+    else:
+        nicedir2 = nicedir
     if rhost == '-':
         rhost = None
     if not rhost:
@@ -17,11 +23,14 @@ def connect(rhost):
         # can't exec *safely* using argv, because *both* ssh and 'sh -c'
         # allow shellquoting.  So we end up having to double-shellquote
         # stuff here.
-        escapedir = re.sub(r'([^\w/])', r'\\\\\\\1', nicedir)
+        escapedir  = re.sub(r'([^\w/])', r'\\\\\\\1', nicedir)
+        escapedir2 = re.sub(r'([^\w/])', r'\\\\\\\1', nicedir2)
         cmd = r"""
-                   sh -c PATH=%s:'$PATH exec sshuttle --server%s'
-               """ % (escapedir, ' -v' * (helpers.verbose or 0))
+                   sh -c PATH=%s:'$HOME'/%s:'$PATH exec sshuttle --server%s'
+               """ % (escapedir, escapedir2,
+                      ' -v' * (helpers.verbose or 0))
         argv = ['ssh', rhost, '--', cmd.strip()]
+        debug2('executing: %r\n' % argv)
     (s1,s2) = socket.socketpair()
     def setup():
         # runs in the child process