# 
# 
# patch "tracvc/mtn/automate.py"
#  from [dc3b66c7286e7f39c8dbb07f671ef6cdb0a28066]
#    to [a0a5a0fa90e6b72944f93064851ab6d28cea49f4]
# 
# patch "tracvc/mtn/backend.py"
#  from [9218c82bd3917f1d436f66e145a0249ddc585a5c]
#    to [5256840759d369117cfb6c04143fe1c35f3192b8]
# 
============================================================
--- tracvc/mtn/automate.py	dc3b66c7286e7f39c8dbb07f671ef6cdb0a28066
+++ tracvc/mtn/automate.py	a0a5a0fa90e6b72944f93064851ab6d28cea49f4
@@ -23,14 +23,16 @@
 """
 
 import os, re, time, calendar
+try:
+    import threading as _threading
+except ImportError:
+    import dummy_threading as _threading
 import basic_io
 
-
 MT_BINARY = "/usr/bin/mtn" # fixme: default, make this configurable
 TAGS_RULE = re.compile(r"^(?P<tag>.*?) (?P<rev>[0-9a-f]{40}) (?P<key>.*)\n", re.MULTILINE)
+REV_RULE = re.compile('^[0-9a-f]{40}$')
 
-
-
 class Connection:
     """Starts monotone and communicates with it through a pipe."""
 
@@ -50,6 +52,7 @@
 
 class List:
     """General interface to the 'list' command."""
+
     def __init__(self, db, binary):
         self.db = db
         self.binary = binary
@@ -64,7 +67,8 @@
 
     def __init__(self, db, binary):
         self.conn = Connection(db, "automate stdio", binary)
-
+        self.lock = _threading.Lock()
+    
     def _read_until_colon(self):
         result = ''
         while True:
@@ -73,8 +77,9 @@
             result += char
         return result
     
-    # we must not block, so be careful to read only what's expected
     def _read_packet(self):
+        # we must not block, so be careful to read only what's
+        # expected
         cmd_nr = self._read_until_colon()
         status = int(self._read_until_colon())
         cont   = self._read_until_colon()
@@ -83,6 +88,7 @@
         return status, cont, val
 
     def _get_result(self):
+        """Read and concatenate the result packages."""
         result, cont = ('', '')
         while cont != 'l':
             status, cont, val = self._read_packet()
@@ -90,6 +96,7 @@
         return status, result
 
     def _write_cmd(self, cmd, args):
+        """Assemble command and args and send it to mtn."""
         def lstring(str):
             return "%d:%s" % (len(str), str)
         cmdstring = "l" + lstring(cmd)
@@ -101,8 +108,13 @@
 
     def command(self, cmd, *args):
         """Send a command to mtn. Returns a tuple (status, result)."""
+        # critical region: only one thread may send a command and read
+        # back the result at a time
+        self.lock.acquire()
         self._write_cmd(cmd, args)
-        return self._get_result()
+        status, result = self._get_result()
+        self.lock.release()
+        return status, result
 
 
 class MTN:
@@ -160,7 +172,6 @@
 
     def select(self, selector):
         """Returns a list of revisions selected by the selector."""
-        #self.log.debug('select: %s', selector)
         status, result = self.automate.command("select", selector)
         if status == 0: return result.splitlines()
         else: return []
============================================================
--- tracvc/mtn/backend.py	9218c82bd3917f1d436f66e145a0249ddc585a5c
+++ tracvc/mtn/backend.py	5256840759d369117cfb6c04143fe1c35f3192b8
@@ -28,9 +28,7 @@
 from trac.core import *
 from cStringIO import StringIO
 from automate import MTN
-import re
 
-REV = re.compile('^[0-9a-f]{40}$')
 
 class MonotoneConnector(Component):
 
@@ -119,15 +117,20 @@
         node at that revision is returned, otherwise the latest version
         of the node is returned.
         """
-        return MonotoneNode(self.mtn, rev, path)
+        # Note: in an mtn repository, there might be many file
+        # hierarchies, so it makes no sense to ask for the latest
+        # version of a path.
+        return MonotoneNode(self.mtn, rev or self.get_youngest_rev(), path)
 
     def get_oldest_rev(self):
         """
         Return the oldest revision stored in the repository.
         Here: Return the oldest root.
         """
-        revs = dict([(self.mtn.dates(rev)[0], rev) for rev in self.mtn.roots()])
-        return revs[sorted(revs.keys())[0]]
+        roots = dict([(self.mtn.dates(rev)[0], rev) for rev in self.mtn.roots()])
+        dates = roots.keys()
+        dates.sort()
+        return roots[dates[0]]
 
     def get_youngest_rev(self):
         """
@@ -135,7 +138,9 @@
         Here: Return the youngest leave.
         """
         leaves = dict([(self.mtn.dates(rev)[-1], rev) for rev in self.mtn.leaves()])
-        return leaves[sorted(leaves.keys())[-1]]
+        dates = leaves.keys()
+        dates.sort()
+        return leaves[dates[-1]]
 
     def previous_rev(self, rev):
         """
@@ -182,9 +187,11 @@
         Return a canonical representation of a revision in the repos.
         'None' is a valid revision value and represents the youngest revision.
         """
-        if REV.match(rev): return rev
-        revs = self.mtn.select(rev)
-        return revs and revs[0] or self.get_youngest_rev()
+        if rev:
+            revs = self.mtn.select(rev)
+            if revs:
+                return revs[0]
+        return self.get_youngest_rev()
 
     def short_rev(self, rev):
         """