diff --git a/drover.py b/drover.py
index 472f3ee07f..9f81287eb6 100644
--- a/drover.py
+++ b/drover.py
@@ -2,76 +2,98 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import os
-import re
 import subprocess
 import sys
+import re
+import os
 import webbrowser
 
+export_map_ = None
+files_info_ = None
+delete_map_ = None
+file_pattern_ =  r"[ ]+([MADUC])[ ]+/((?:trunk|branches/\d+)/src(.*)/(.*))"
 
 def deltree(root):
-  """Removes a given directory."""
+  """
+  Removes a given directory
+  """
   if (not os.path.exists(root)):
     return
-
+  
   if sys.platform == 'win32':
     os.system('rmdir /S /Q ' + root.replace('/','\\'))
   else:
     for name in os.listdir(root):
-      path = os.path.join(root, name)
-      if os.path.isdir(path):
-        deltree(path)
-      else:
-        os.unlink(path)
+        path = os.path.join(root, name)
+        if os.path.isdir(path):
+            deltree(path)
+        else:
+            os.unlink(path)
     os.rmdir(root)
 
-
 def clobberDir(dir):
-  """Removes a given directory."""
-
+  """
+  Removes a given directory
+  """
+  
   if (os.path.exists(dir)):
-    print dir + " directory found, deleting"
-    # The following line was removed due to access controls in Windows
-    # which make os.unlink(path) calls impossible.
-    # deltree(dir)
-    os.system('rmdir /S /Q ' + dir.replace('/','\\'))
-
+      print dir + " directory found, deleting"
+      #The following line was removed due to access controls in Windows
+      #which make os.unlink(path) calls impossible.
+      #deltree(dir)
+      os.system('rmdir /S /Q ' + dir.replace('/','\\'))
 
 def gclUpload(revision, author):
-  command = ("gcl upload " + str(revision) +
+  command = ("gcl upload " + str(revision) + 
              " --send_mail --no_try --no_presubmit --reviewers=" + author)
   os.system(command)
-#  subprocess.Popen(command,
-#                   shell=True,
-#                   stdout=None,
-#                   stderr=subprocess.PIPE)
-#                              stderr=subprocess.PIPE).stdout.readlines()
-#  for line in svn_info:
-#    match = re.search(r"Issue created. URL: (http://.+)", line)
-#    if match:
-#      return match.group(1)
-  return None
-
 
-def getAuthor(url, revision):
+def getSVNInfo(url, revision):
   command = 'svn info ' + url + "@"+str(revision)
-  svn_info = subprocess.Popen(command,
-                              shell=True,
-                              stdout=subprocess.PIPE,
-                              stderr=subprocess.PIPE).stdout.readlines()
+  svn_info = subprocess.Popen(command, 
+                              shell=True, 
+                              stdout=subprocess.PIPE, 
+                              stderr=subprocess.PIPE).stdout.readlines()                              
+  rtn = {}                              
   for line in svn_info:
-    match = re.search(r"Last Changed Author: (.+)", line)
+    match = re.search(r"(.*?):(.*)", line)
     if match:
-      return match.group(1)
-  return None
+    	rtn[match.group(1).strip()]=match.group(2).strip()
+  
+  return rtn
 
+def getAuthor(url, revision):
+  info = getSVNInfo(url, revision)
+  
+  if (info.has_key("Last Changed Author")):
+    return info["Last Changed Author"]
+    
+  return None
 
+def isSVNFile(url, revision):
+  info = getSVNInfo(url, revision)
+  
+  if (info.has_key("Node Kind")):
+    if (info["Node Kind"] == "file"): return True
+  
+  return False 
+
+def isSVNDirectory(url, revision):
+  info = getSVNInfo(url, revision)
+  
+  if (info.has_key("Node Kind")):
+    if (info["Node Kind"] == "directory"): return True
+  
+  return False 
+  
 def getRevisionLog(url, revision):
-  """Takes an svn url and gets the associated revision. """
+  """
+  Takes an svn url and gets the associated revision.
+  """
   command = 'svn log ' + url + " -r"+str(revision)
-  svn_info = subprocess.Popen(command,
-                              shell=True,
-                              stdout=subprocess.PIPE,
+  svn_info = subprocess.Popen(command, 
+                              shell=True, 
+                              stdout=subprocess.PIPE, 
                               stderr=subprocess.PIPE).stdout.readlines()
   rtn= ""
   pos = 0
@@ -83,136 +105,225 @@ def getRevisionLog(url, revision):
 
   return rtn
 
+def checkoutRevision(url, revision, branch_url, revert=False):
+  files_info = getFileInfo(url, revision) 
+  paths = getBestMergePaths2(files_info, revision)
+  export_map = getBestExportPathsMap2(files_info, revision)
+  
+  command = 'svn checkout -N ' + branch_url
+  print command
+  os.system(command)
 
-def checkoutRevision(url, revision, branch_url):
-  paths = getBestMergePaths(url, revision)
-  deltree('./src')
-  if not os.path.exists('./src'):
-    command = 'svn checkout -N ' + branch_url
-    print command
-    os.system(command)
+  match = re.search(r"svn://.*/(.*)", branch_url)
+  
+  if match:
+    os.chdir(match.group(1))
 
-  # This line is extremely important due to the way svn behaves in the
-  # set-depths action. If parents aren't handled before children, the child
-  # directories get clobbered and the merge step fails.
+  #This line is extremely important due to the way svn behaves in the set-depths
+  #action.  If parents aren't handled before children, the child directories get
+  #clobbered and the merge step fails.
   paths.sort()
+
+  #Checkout the directories that already exist  
   for path in paths:
-    subpaths = path.split('/')
-    subpaths.pop(0)
-    base = './src'
-    for subpath in subpaths:
-      base += '/' + subpath
-      if not os.path.exists(base):
-        command = ('svn update --depth empty ' + base)
-        print command
-        os.system(command)
-      else:
-        print "Found " + base
-
-  for file in getFilesInRevision(url, revision):
-   # Prevent the tool from clobbering the src directory.
+     if (export_map.has_key(path) and not revert):
+       print "Exclude new directory " + path
+       continue
+     subpaths = path.split('/')
+     subpaths.pop(0)
+     base = ''
+     for subpath in subpaths:
+       base += '/' + subpath
+       #This logic ensures that you don't empty out any directories     
+       if not os.path.exists("." + base):
+         command = ('svn update --depth empty ' + "." + base) 
+         print command
+         os.system(command)
+    
+  if (revert):
+    files = getAllFilesInRevision(files_info)
+  else:
+    files = getExistingFilesInRevision(files_info)
+  
+  for file in files:
+   #Prevent the tool from clobbering the src directory  
     if (file == ""):
       continue
-    command = ('svn up ./src' + file)
+    command = ('svn up ".' + file + '"')
     print command
     os.system(command)
-
-
-def mergeRevision(url, revision, ignoreAncestry=False):
+  
+def mergeRevision(url, revision):
   paths = getBestMergePaths(url, revision)
+  export_map = getBestExportPathsMap(url, revision)
+  
   for path in paths:
+    if export_map.has_key(path):
+      continue
     command = ('svn merge -N -r ' + str(revision-1) + ":" + str(revision) + " ")
-    if (ignoreAncestry):
-      command = command + " --ignore-ancestry "
-    command = command + url + path + " ./src" + path
+    command = command + url + path + "@" + str(revision) + " ." + path
+     
     print command
     os.system(command)
 
-
-def revertRevision(url, revision):
-  paths = getBestMergePaths(url, revision)
+def exportRevision(url, revision):
+  paths = getBestExportPathsMap(url, revision).keys()
+  
+  paths.sort()
+  
   for path in paths:
-    command = ('svn merge -N -r ' + str(revision) + ":" + str(revision-1) +
-               " " + url + path + " ./src" + path)
+    command = ('svn export -N ' + url + path + "@" + str(revision) + " ." 
+              + path)
     print command
     os.system(command)
+    
+    command = ('svn add .' + path)
+    print command 
+    os.system(command)
 
+def deleteRevision(url, revision):
+  paths = getBestDeletePathsMap(url, revision).keys()
+  paths.sort()
+  paths.reverse()
+  
+  for path in paths:
+    command = ("svn delete ." + path) 
+    print command
+    os.system(command)
 
-def getBestMergePaths(url, revision):
-  """Takes an svn url and gets the associated revision."""
-  command = 'svn log ' + url + " -r "+str(revision) + " -v"
-  svn_info = subprocess.Popen(command,
-                              shell=True,
-                              stdout=subprocess.PIPE,
-                              stderr=subprocess.PIPE).stdout.readlines()
-  map = {}
-  for line in svn_info:
-    match = re.search(r"[\n\r ]+[MADUC][\n\r ]+/(?:trunk|branches/\d+)/src([^ ]*)/[^ ]+", line)
-    if match:
-      map[match.group(1)] = match.group(1)
-
-  return map.keys()
 
+def revertExportRevision(url, revision):
+  paths = getBestExportPathsMap(url, revision).keys()
+  paths.sort()
+  paths.reverse()
+  
+  for path in paths:
+    command = ("svn delete ." + path) 
+    print command
+    os.system(command)
 
-def getFilesInRevision(url, revision):
-  """Takes an svn url and gets the associated revision."""
-  command = 'svn log ' + url + " -r "+str(revision) + " -v"
-  svn_info = subprocess.Popen(command,
-                              shell=True,
-                              stdout=subprocess.PIPE,
+def revertRevision(url, revision):
+  paths = getBestMergePaths(url, revision)
+  for path in paths:
+    command = ('svn merge -N -r ' + str(revision) + ":" + str(revision-1) + 
+                " " + url + path + " ." + path) 
+    print command
+    os.system(command)
+    
+def getFileInfo(url, revision):
+  global files_info_, file_pattern_
+  
+  if (files_info_ != None):
+    return files_info_
+
+  command = 'svn log ' + url + " -r " + str(revision) + " -v"
+  svn_log = subprocess.Popen(command, 
+                              shell=True, 
+                              stdout=subprocess.PIPE, 
                               stderr=subprocess.PIPE).stdout.readlines()
-  map = {}
-  for line in svn_info:
-    match = re.search(r"[\n\r ]+[MADUC][\n\r ]+/(?:trunk|branches/\d+)/src([^ ]*)/([^ ]+)", line)
+                              
+  rtn = []                              
+  for line in svn_log:
+    #A workaround to dump the (from .*) stuff, regex not so friendly in the 2nd
+    #pass...
+    match = re.search(r"(.*) \(from.*\)", line)
     if match:
-      map[match.group(1) + "/" + match.group(2)] = match.group(1) + "/" + match.group(2)
+      line = match.group(1)
+    match = re.search(file_pattern_, line)
+    if match:
+      rtn.append([match.group(1).strip(), match.group(2).strip(),
+                 match.group(3).strip(),match.group(4).strip()])
 
-  return map.keys()
+  files_info_ = rtn  
+  return rtn
 
+def getBestMergePaths(url, revision):
+  """
+  Takes an svn url and gets the associated revision.
+  """
+  return getBestMergePaths2(getFileInfo(url, revision), revision)
 
-def getBestMergePath(url, revision):
-  """Takes an svn url and gets the associated revision."""
-  command = 'svn log ' + url + " -r "+str(revision) + " -v"
-  svn_info = subprocess.Popen(command,
-                              shell=True,
-                              stdout=subprocess.PIPE,
-                              stderr=subprocess.PIPE).stdout.readlines()
-  best_path = None
-  for line in svn_info:
-    match = re.search(r"[\n\r ]+[MADUC][\n\r ]+/.*/src(.*)/.+", line)
-    if match:
-      if (best_path == None):
-        best_path = match.group(1)
-      else:
-        best_path = leastPath(match.group(1),best_path)
-
-  return best_path
-
-
-def leastPath(a, b):
-  if (not a) or (a == ""):
-    return ""
-  if (b == ""):
-    return ""
-  if (not b):
-    return a
-
-  a_list = a.lstrip("/").split("/")
-  b_list = b.lstrip("/").split("/")
-  last_match = ""
-  while((len(a_list) != 0) and (len(b_list) != 0)):
-    a_value = a_list.pop(0)
-    b_value = b_list.pop(0)
-    if (a_value == b_value):
-      last_match = last_match + "/" + a_value
-    else:
-      break
+def getBestMergePaths2(files_info, revision):
+  """
+  Takes an svn url and gets the associated revision.
+  """
 
-  return last_match
+  map = dict()
+  for file_info in files_info:
+    map[file_info[2]] = file_info[2]
 
+  return map.keys()
+
+def getBestExportPathsMap(url, revision):
+  return getBestExportPathsMap2(getFileInfo(url, revision), revision)
+    
+def getBestExportPathsMap2(files_info, revision):
+  """
+  Takes an svn url and gets the associated revision.
+  """
+  global export_map_
+  
+  if export_map_:
+    return export_map_
+
+  map = dict()
+  for file_info in files_info:
+    if (file_info[0] == "A"):
+      if(isSVNDirectory("svn://chrome-svn/chrome/" + file_info[1], revision)):
+        map[file_info[2] + "/" + file_info[3]] = ""
+
+  export_map_ = map
+        
+  return map
+
+def getBestDeletePathsMap(url, revision):
+  return getBestDeletePathsMap2(getFileInfo(url, revision), revision)  
+
+def getBestDeletePathsMap2(files_info, revision):
+  """
+  Takes an svn url and gets the associated revision.
+  """
+  global delete_map_
+  
+  if delete_map_:
+    return delete_map_
+
+  map = dict()
+  for file_info in files_info:
+    if (file_info[0] == "D"):
+      if(isSVNDirectory("svn://chrome-svn/chrome/" + file_info[1], revision)):
+        map[file_info[2] + "/" + file_info[3]] = ""
+
+  delete_map_ = map
+        
+  return map
+  
+def getExistingFilesInRevision(files_info):
+  """
+  Checks for existing files in the revision, anything that's A will require
+  special treatment (either a merge or an export + add)  
+  """
+  map = []
+  for file_info in files_info:
+    if file_info[0] != "A": 
+      map.append(file_info[2] + "/" + file_info[3])
+
+  return map
+
+def getAllFilesInRevision(files_info):
+  """
+  Checks for existing files in the revision, anything that's A will require
+  special treatment (either a merge or an export + add)  
+  """
+  map = []
+  for file_info in files_info:
+    map.append(file_info[2] + "/" + file_info[3])
+
+  return map
 
 def prompt(question):
   p = None
+  
   while not p:
     print question + " [y|n]:"
     p = sys.stdin.readline()
@@ -221,13 +332,30 @@ def prompt(question):
     elif p.lower().startswith('y'):
       return True
     else:
-      p = None
-
-
+      p = None 
+
+def text_prompt(question, default):
+  print question + " [" + default + "]:"
+  p = sys.stdin.readline()
+  if p.strip() == "":
+    return default
+  return p
+        
 def main(argv=None):
   BASE_URL = "svn://chrome-svn/chrome"
   TRUNK_URL = BASE_URL + "/trunk/src"
-  BRANCH_URL = None
+  BRANCH_URL = BASE_URL + "/branches/$branch/src"
+  DEFAULT_WORKING = "working"
+  SKIP_CHECK_WORKING = True
+  PROMPT_FOR_AUTHOR = False
+  
+  global file_pattern_
+  if os.path.exists("drover.properties"):
+    file = open("drover.properties")
+    exec(file)
+    file.close()
+    if FILE_PATTERN:
+      file_pattern_ = FILE_PATTERN   
 
   if (len(sys.argv) == 1):
     print "WARNING: Please use this tool in an empty directory (or at least one"
@@ -251,45 +379,57 @@ def main(argv=None):
 
   revision = int(sys.argv[1])
   if ((len(sys.argv) >= 4) and (sys.argv[2] in ['--revert','-r'])):
-    BRANCH_URL = BASE_URL + "/branches/" + sys.argv[3] + "/src"
-    url = BRANCH_URL
+    url = BRANCH_URL.replace("$branch", sys.argv[3]) 
   else:
     url = TRUNK_URL
   action = "Merge"
+  
+  working = DEFAULT_WORKING
+  
   command = 'svn log ' + url + " -r "+str(revision) + " -v"
   os.system(command)
+  
   if not prompt("Is this the correct revision?"):
     sys.exit(0)
-
+  
+  if (os.path.exists(working)):
+    if not (SKIP_CHECK_WORKING or prompt("Working directory: '" + working + "' already exists, clobber?")):
+      sys.exit(0)
+    deltree(working)
+  
+  os.makedirs(working)  
+  os.chdir(working)
+  
   if (len(sys.argv) > 1):
      if sys.argv[2] in ['--merge','-m']:
         if (len(sys.argv) != 4):
           print "Please specify the branch # you want (i.e. 182) after --merge"
           sys.exit(0)
-
-        branch_url = "svn://chrome-svn/chrome/branches/" + sys.argv[3] + "/src"
+           
+        branch_url = BRANCH_URL.replace("$branch", sys.argv[3])
+        #Checkout everything but stuff that got added into a new dir
         checkoutRevision(url, revision, branch_url)
+        #Merge everything that changed
         mergeRevision(url, revision)
-     elif sys.argv[2] in ['--mplus','-p']:
-        if (len(sys.argv) != 4):
-          print "Please specify the branch # you want (i.e. 182) after --merge"
-          sys.exit(0)
-        branch_url = "svn://chrome-svn/chrome/branches/" + sys.argv[3] + "/src"
-        checkoutRevision(url, revision, branch_url)
-        mergeRevision(url, revision, True)
+        #"Export" files that were added from the source and add them to branch
+        exportRevision(url, revision)
+        #Delete directories that were deleted (file deletes are handled in the
+        #merge).
+        deleteRevision(url, revision)        
      elif sys.argv[2] in ['--revert','-r']:
        if (len(sys.argv) == 4):
-         url = "svn://chrome-svn/chrome/branches/" + sys.argv[3] + "/src"
-       checkoutRevision(url, revision, url)
+         url = BRANCH_URL.replace("$branch", sys.argv[3])
+       checkoutRevision(url, revision, url, True)
        revertRevision(url, revision)
+       revertExportRevision(url, revision)
        action = "Revert"
      else:
        print "Unknown parameter " + sys.argv[2]
        sys.exit(0)
-
-  os.chdir('./src')
-  # Check the base url so we actually find the author who made the change.
-  author = getAuthor(BASE_URL, revision)
+  
+  #Check the base url so we actually find the author who made the change
+  author = getAuthor(TRUNK_URL, revision)
+  
   filename = str(revision)+".txt"
   out = open(filename,"w")
   out.write(action +" " + str(revision) + " - ")
@@ -297,15 +437,19 @@ def main(argv=None):
   if (author):
     out.write("TBR=" + author)
   out.close()
+  
   os.system('gcl change ' + str(revision) + " " + filename)
   os.unlink(filename)
   print author
   print revision
-  print "gcl upload " + str(revision) + " --send_mail --no_try --no_presubmit --reviewers=" + author
+  print ("gcl upload " + str(revision) + 
+         " --send_mail --no_try --no_presubmit --reviewers=" + author)
   print "gcl commit " + str(revision) + " --no_presubmit --force"
   print "gcl delete " + str(revision)
 
   if prompt("Would you like to upload?"):
+    if PROMPT_FOR_AUTHOR:
+      author = text_prompt("Enter a new author or press enter to accept default", author)
     gclUpload(revision, author)
   else:
     print "Deleting the changelist."
@@ -316,7 +460,6 @@ def main(argv=None):
     os.system("gcl commit " + str(revision) + " --no_presubmit --force")
   else:
     sys.exit(0)
-
-
+  
 if __name__ == "__main__":
-  sys.exit(main())
+  sys.exit(main())
\ No newline at end of file