diff --git a/docs/manifest-format.txt b/docs/manifest-format.txt
index e48b75f..f187bfa 100644
--- a/docs/manifest-format.txt
+++ b/docs/manifest-format.txt
@@ -35,6 +35,7 @@
     <!ATTLIST remote alias        CDATA #IMPLIED>
     <!ATTLIST remote fetch        CDATA #REQUIRED>
     <!ATTLIST remote review       CDATA #IMPLIED>
+    <!ATTLIST remote revision     CDATA #IMPLIED>
 
     <!ELEMENT default (EMPTY)>
     <!ATTLIST default remote      IDREF #IMPLIED>
@@ -112,6 +113,10 @@
 are uploaded to by `repo upload`.  This attribute is optional;
 if not specified then `repo upload` will not function.
 
+Attribute `revision`: Name of a Git branch (e.g. `master` or
+`refs/heads/master`). Remotes with their own revision will override
+the default revision.
+
 Element default
 ---------------
 
@@ -208,7 +213,8 @@
 (e.g. just "master") or absolute (e.g. "refs/heads/master").
 Tags and/or explicit SHA-1s should work in theory, but have not
 been extensively tested.  If not supplied the revision given by
-the default element is used.
+the remote element is used if applicable, else the default
+element is used.
 
 Attribute `dest-branch`: Name of a Git branch (e.g. `master`).
 When using `repo upload`, changes will be submitted for code
diff --git a/error.py b/error.py
index 7e52b01..ff948f9 100644
--- a/error.py
+++ b/error.py
@@ -24,6 +24,13 @@
 class NoManifestException(Exception):
   """The required manifest does not exist.
   """
+  def __init__(self, path, reason):
+    super(NoManifestException, self).__init__()
+    self.path = path
+    self.reason = reason
+
+  def __str__(self):
+    return self.reason
 
 class EditorError(Exception):
   """Unspecified error from the user's text editor.
diff --git a/git_config.py b/git_config.py
index c1a6b55..a667b3f 100644
--- a/git_config.py
+++ b/git_config.py
@@ -15,8 +15,8 @@
 
 from __future__ import print_function
 
+import json
 import os
-import pickle
 import re
 import subprocess
 import sys
@@ -80,7 +80,7 @@
     return cls(configfile = os.path.join(gitdir, 'config'),
                defaults = defaults)
 
-  def __init__(self, configfile, defaults=None, pickleFile=None):
+  def __init__(self, configfile, defaults=None, jsonFile=None):
     self.file = configfile
     self.defaults = defaults
     self._cache_dict = None
@@ -88,12 +88,11 @@
     self._remotes = {}
     self._branches = {}
 
-    if pickleFile is None:
-      self._pickle = os.path.join(
+    self._json = jsonFile
+    if self._json is None:
+      self._json = os.path.join(
         os.path.dirname(self.file),
-        '.repopickle_' + os.path.basename(self.file))
-    else:
-      self._pickle = pickleFile
+        '.repo_' + os.path.basename(self.file) + '.json')
 
   def Has(self, name, include_defaults = True):
     """Return true if this configuration file has the key.
@@ -248,50 +247,41 @@
     return self._cache_dict
 
   def _Read(self):
-    d = self._ReadPickle()
+    d = self._ReadJson()
     if d is None:
       d = self._ReadGit()
-      self._SavePickle(d)
+      self._SaveJson(d)
     return d
 
-  def _ReadPickle(self):
+  def _ReadJson(self):
     try:
-      if os.path.getmtime(self._pickle) \
+      if os.path.getmtime(self._json) \
       <= os.path.getmtime(self.file):
-        os.remove(self._pickle)
+        os.remove(self._json)
         return None
     except OSError:
       return None
     try:
-      Trace(': unpickle %s', self.file)
-      fd = open(self._pickle, 'rb')
+      Trace(': parsing %s', self.file)
+      fd = open(self._json)
       try:
-        return pickle.load(fd)
+        return json.load(fd)
       finally:
         fd.close()
-    except EOFError:
-      os.remove(self._pickle)
-      return None
-    except IOError:
-      os.remove(self._pickle)
-      return None
-    except pickle.PickleError:
-      os.remove(self._pickle)
+    except (IOError, ValueError):
+      os.remove(self._json)
       return None
 
-  def _SavePickle(self, cache):
+  def _SaveJson(self, cache):
     try:
-      fd = open(self._pickle, 'wb')
+      fd = open(self._json, 'w')
       try:
-        pickle.dump(cache, fd, pickle.HIGHEST_PROTOCOL)
+        json.dump(cache, fd, indent=2)
       finally:
         fd.close()
-    except IOError:
-      if os.path.exists(self._pickle):
-        os.remove(self._pickle)
-    except pickle.PickleError:
-      if os.path.exists(self._pickle):
-        os.remove(self._pickle)
+    except (IOError, TypeError):
+      if os.path.exists(self.json):
+        os.remove(self._json)
 
   def _ReadGit(self):
     """
diff --git a/main.py b/main.py
index 3661776..72fb39b 100755
--- a/main.py
+++ b/main.py
@@ -129,8 +129,15 @@
             file=sys.stderr)
       return 1
 
-    copts, cargs = cmd.OptionParser.parse_args(argv)
-    copts = cmd.ReadEnvironmentOptions(copts)
+    try:
+      copts, cargs = cmd.OptionParser.parse_args(argv)
+      copts = cmd.ReadEnvironmentOptions(copts)
+    except NoManifestException as e:
+      print('error: in `%s`: %s' % (' '.join([name] + argv), str(e)),
+        file=sys.stderr)
+      print('error: manifest missing or unreadable -- please run init',
+            file=sys.stderr)
+      return 1
 
     if not gopts.no_pager and not isinstance(cmd, InteractiveCommand):
       config = cmd.manifest.globalConfig
@@ -146,15 +153,13 @@
     start = time.time()
     try:
       result = cmd.Execute(copts, cargs)
-    except DownloadError as e:
-      print('error: %s' % str(e), file=sys.stderr)
-      result = 1
-    except ManifestInvalidRevisionError as e:
-      print('error: %s' % str(e), file=sys.stderr)
-      result = 1
-    except NoManifestException as e:
-      print('error: manifest required for this command -- please run init',
-            file=sys.stderr)
+    except (DownloadError, ManifestInvalidRevisionError,
+        NoManifestException) as e:
+      print('error: in `%s`: %s' % (' '.join([name] + argv), str(e)),
+        file=sys.stderr)
+      if isinstance(e, NoManifestException):
+        print('error: manifest missing or unreadable -- please run init',
+              file=sys.stderr)
       result = 1
     except NoSuchProjectError as e:
       if e.name:
diff --git a/manifest_xml.py b/manifest_xml.py
index 3c8fadd..fdc3177 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -63,12 +63,14 @@
                alias=None,
                fetch=None,
                manifestUrl=None,
-               review=None):
+               review=None,
+               revision=None):
     self.name = name
     self.fetchUrl = fetch
     self.manifestUrl = manifestUrl
     self.remoteAlias = alias
     self.reviewUrl = review
+    self.revision = revision
     self.resolvedFetchUrl = self._resolveFetchUrl()
 
   def __eq__(self, other):
@@ -159,6 +161,8 @@
       e.setAttribute('alias', r.remoteAlias)
     if r.reviewUrl is not None:
       e.setAttribute('review', r.reviewUrl)
+    if r.revision is not None:
+      e.setAttribute('revision', r.revision)
 
   def Save(self, fd, peg_rev=False, peg_rev_upstream=True):
     """Write the current manifest out to the given file descriptor.
@@ -240,7 +244,8 @@
       if d.remote:
         remoteName = d.remote.remoteAlias or d.remote.name
       if not d.remote or p.remote.name != remoteName:
-        e.setAttribute('remote', p.remote.name)
+        remoteName = p.remote.name
+        e.setAttribute('remote', remoteName)
       if peg_rev:
         if self.IsMirror:
           value = p.bare_git.rev_parse(p.revisionExpr + '^0')
@@ -252,8 +257,10 @@
           # isn't our value, and the if the default doesn't already have that
           # covered.
           e.setAttribute('upstream', p.revisionExpr)
-      elif not d.revisionExpr or p.revisionExpr != d.revisionExpr:
-        e.setAttribute('revision', p.revisionExpr)
+      else:
+        revision = self.remotes[remoteName].revision or d.revisionExpr
+        if not revision or revision != p.revisionExpr:
+          e.setAttribute('revision', p.revisionExpr)
 
       for c in p.copyfiles:
         ce = doc.createElement('copyfile')
@@ -261,6 +268,12 @@
         ce.setAttribute('dest', c.dest)
         e.appendChild(ce)
 
+      for l in p.linkfiles:
+        le = doc.createElement('linkfile')
+        le.setAttribute('src', l.src)
+        le.setAttribute('dest', l.dest)
+        e.appendChild(le)
+
       default_groups = ['all', 'name:%s' % p.name, 'path:%s' % p.relpath]
       egroups = [g for g in p.groups if g not in default_groups]
       if egroups:
@@ -304,7 +317,7 @@
   @property
   def projects(self):
     self._Load()
-    return self._paths.values()
+    return list(self._paths.values())
 
   @property
   def remotes(self):
@@ -586,8 +599,11 @@
     review = node.getAttribute('review')
     if review == '':
       review = None
+    revision = node.getAttribute('revision')
+    if revision == '':
+      revision = None
     manifestUrl = self.manifestProject.config.GetString('remote.origin.url')
-    return _XmlRemote(name, alias, fetch, manifestUrl, review)
+    return _XmlRemote(name, alias, fetch, manifestUrl, review, revision)
 
   def _ParseDefault(self, node):
     """
@@ -680,7 +696,7 @@
       raise ManifestParseError("no remote for project %s within %s" %
             (name, self.manifestFile))
 
-    revisionExpr = node.getAttribute('revision')
+    revisionExpr = node.getAttribute('revision') or remote.revision
     if not revisionExpr:
       revisionExpr = self._default.revisionExpr
     if not revisionExpr:
@@ -765,6 +781,8 @@
     for n in node.childNodes:
       if n.nodeName == 'copyfile':
         self._ParseCopyFile(project, n)
+      if n.nodeName == 'linkfile':
+        self._ParseLinkFile(project, n)
       if n.nodeName == 'annotation':
         self._ParseAnnotation(project, n)
       if n.nodeName == 'project':
@@ -814,6 +832,14 @@
       # dest is relative to the top of the tree
       project.AddCopyFile(src, dest, os.path.join(self.topdir, dest))
 
+  def _ParseLinkFile(self, project, node):
+    src = self._reqatt(node, 'src')
+    dest = self._reqatt(node, 'dest')
+    if not self.IsMirror:
+      # src is project relative;
+      # dest is relative to the top of the tree
+      project.AddLinkFile(src, dest, os.path.join(self.topdir, dest))
+
   def _ParseAnnotation(self, project, node):
     name = self._reqatt(node, 'name')
     value = self._reqatt(node, 'value')
@@ -856,10 +882,8 @@
     fromProjects = self.paths
     toProjects = manifest.paths
 
-    fromKeys = fromProjects.keys()
-    fromKeys.sort()
-    toKeys = toProjects.keys()
-    toKeys.sort()
+    fromKeys = sorted(fromProjects.keys())
+    toKeys = sorted(toProjects.keys())
 
     diff = {'added': [], 'removed': [], 'changed': [], 'unreachable': []}
 
diff --git a/project.py b/project.py
index d07b521..460bf31 100644
--- a/project.py
+++ b/project.py
@@ -231,14 +231,40 @@
       except IOError:
         _error('Cannot copy file %s to %s', src, dest)
 
+class _LinkFile:
+  def __init__(self, src, dest, abssrc, absdest):
+    self.src = src
+    self.dest = dest
+    self.abs_src = abssrc
+    self.abs_dest = absdest
+
+  def _Link(self):
+    src = self.abs_src
+    dest = self.abs_dest
+    # link file if it does not exist or is out of date
+    if not os.path.islink(dest) or os.readlink(dest) != src:
+      try:
+        # remove existing file first, since it might be read-only
+        if os.path.exists(dest):
+          os.remove(dest)
+        else:
+          dest_dir = os.path.dirname(dest)
+          if not os.path.isdir(dest_dir):
+            os.makedirs(dest_dir)
+        os.symlink(src, dest)
+      except IOError:
+        _error('Cannot link file %s to %s', src, dest)
+
 class RemoteSpec(object):
   def __init__(self,
                name,
                url = None,
-               review = None):
+               review = None,
+               revision = None):
     self.name = name
     self.url = url
     self.review = review
+    self.revision = revision
 
 class RepoHook(object):
   """A RepoHook contains information about a script to run as a hook.
@@ -414,7 +440,8 @@
       # and  convert to a HookError w/ just the failing traceback.
       context = {}
       try:
-        execfile(self._script_fullpath, context)
+        exec(compile(open(self._script_fullpath).read(),
+                     self._script_fullpath, 'exec'), context)
       except Exception:
         raise HookError('%s\nFailed to import %s hook; see traceback above.' % (
                         traceback.format_exc(), self._hook_type))
@@ -555,6 +582,7 @@
 
     self.snapshots = {}
     self.copyfiles = []
+    self.linkfiles = []
     self.annotations = []
     self.config = GitConfig.ForRepository(
                     gitdir = self.gitdir,
@@ -1040,7 +1068,7 @@
       except OSError as e:
         print("warn: Cannot remove archive %s: "
               "%s" % (tarpath, str(e)), file=sys.stderr)
-      self._CopyFiles()
+      self._CopyAndLinkFiles()
       return True
 
     if is_new is None:
@@ -1078,17 +1106,12 @@
       elif self.manifest.default.sync_c:
         current_branch_only = True
 
-    is_sha1 = False
-    if ID_RE.match(self.revisionExpr) is not None:
-      is_sha1 = True
-    if is_sha1 and self._CheckForSha1():
-      # Don't need to fetch since we already have this revision
-      return True
-
-    if not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir,
-                             current_branch_only=current_branch_only,
-                             no_tags=no_tags):
-      return False
+    has_sha1 = ID_RE.match(self.revisionExpr) and self._CheckForSha1()
+    if (not has_sha1  #Need to fetch since we don't already have this revision
+        and not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir,
+                                  current_branch_only=current_branch_only,
+                                  no_tags=no_tags)):
+          return False
 
     if self.worktree:
       self._InitMRef()
@@ -1103,9 +1126,11 @@
   def PostRepoUpgrade(self):
     self._InitHooks()
 
-  def _CopyFiles(self):
+  def _CopyAndLinkFiles(self):
     for copyfile in self.copyfiles:
       copyfile._Copy()
+    for linkfile in self.linkfiles:
+      linkfile._Link()
 
   def GetCommitRevisionId(self):
     """Get revisionId of a commit.
@@ -1152,7 +1177,7 @@
 
     def _doff():
       self._FastForward(revid)
-      self._CopyFiles()
+      self._CopyAndLinkFiles()
 
     head = self.work_git.GetHead()
     if head.startswith(R_HEADS):
@@ -1188,7 +1213,7 @@
       except GitError as e:
         syncbuf.fail(self, e)
         return
-      self._CopyFiles()
+      self._CopyAndLinkFiles()
       return
 
     if head == revid:
@@ -1210,7 +1235,7 @@
       except GitError as e:
         syncbuf.fail(self, e)
         return
-      self._CopyFiles()
+      self._CopyAndLinkFiles()
       return
 
     upstream_gain = self._revlist(not_rev(HEAD), revid)
@@ -1283,12 +1308,12 @@
     if cnt_mine > 0 and self.rebase:
       def _dorebase():
         self._Rebase(upstream = '%s^1' % last_mine, onto = revid)
-        self._CopyFiles()
+        self._CopyAndLinkFiles()
       syncbuf.later2(self, _dorebase)
     elif local_changes:
       try:
         self._ResetHard(revid)
-        self._CopyFiles()
+        self._CopyAndLinkFiles()
       except GitError as e:
         syncbuf.fail(self, e)
         return
@@ -1301,6 +1326,12 @@
     abssrc = os.path.join(self.worktree, src)
     self.copyfiles.append(_CopyFile(src, dest, abssrc, absdest))
 
+  def AddLinkFile(self, src, dest, absdest):
+    # dest should already be an absolute path, but src is project relative
+    # make src an absolute path
+    abssrc = os.path.join(self.worktree, src)
+    self.linkfiles.append(_LinkFile(src, dest, abssrc, absdest))
+
   def AddAnnotation(self, name, value, keep):
     self.annotations.append(_Annotation(name, value, keep))
 
@@ -1629,7 +1660,8 @@
 
       remote = RemoteSpec(self.remote.name,
                           url = url,
-                          review = self.remote.review)
+                          review = self.remote.review,
+                          revision = self.remote.revision)
       subproject = Project(manifest = self.manifest,
                            name = name,
                            remote = remote,
@@ -1674,6 +1706,7 @@
     if command.Wait() != 0:
       raise GitError('git archive %s: %s' % (self.name, command.stderr))
 
+
   def _RemoteFetch(self, name=None,
                    current_branch_only=False,
                    initial=False,
@@ -1683,11 +1716,17 @@
 
     is_sha1 = False
     tag_name = None
+    depth = None
 
-    if self.clone_depth:
-      depth = self.clone_depth
-    else:
-      depth = self.manifest.manifestProject.config.GetString('repo.depth')
+    # The depth should not be used when fetching to a mirror because
+    # it will result in a shallow repository that cannot be cloned or
+    # fetched from.
+    if not self.manifest.IsMirror:
+      if self.clone_depth:
+        depth = self.clone_depth
+      else:
+        depth = self.manifest.manifestProject.config.GetString('repo.depth')
+
     if depth:
       current_branch_only = True
 
@@ -1763,26 +1802,37 @@
       cmd.append('--update-head-ok')
     cmd.append(name)
 
+    # If using depth then we should not get all the tags since they may
+    # be outside of the depth.
+    if no_tags or depth:
+      cmd.append('--no-tags')
+    else:
+      cmd.append('--tags')
+
+    spec = []
     if not current_branch_only:
       # Fetch whole repo
-      # If using depth then we should not get all the tags since they may
-      # be outside of the depth.
-      if no_tags or depth:
-        cmd.append('--no-tags')
-      else:
-        cmd.append('--tags')
-
-      cmd.append(str((u'+refs/heads/*:') + remote.ToLocal('refs/heads/*')))
+      spec.append(str((u'+refs/heads/*:') + remote.ToLocal('refs/heads/*')))
     elif tag_name is not None:
-      cmd.append('tag')
-      cmd.append(tag_name)
+      spec.append('tag')
+      spec.append(tag_name)
     else:
       branch = self.revisionExpr
       if is_sha1:
         branch = self.upstream
       if branch.startswith(R_HEADS):
         branch = branch[len(R_HEADS):]
-      cmd.append(str((u'+refs/heads/%s:' % branch) + remote.ToLocal('refs/heads/%s' % branch)))
+      spec.append(str((u'+refs/heads/%s:' % branch) + remote.ToLocal('refs/heads/%s' % branch)))
+    cmd.extend(spec)
+
+    shallowfetch = self.config.GetString('repo.shallowfetch')
+    if shallowfetch and shallowfetch != ' '.join(spec):
+      GitCommand(self, ['fetch', '--unshallow', name] + shallowfetch.split(),
+                 bare=True, ssh_proxy=ssh_proxy).Wait()
+    if depth:
+        self.config.SetString('repo.shallowfetch', ' '.join(spec))
+    else:
+        self.config.SetString('repo.shallowfetch', None)
 
     ok = False
     for _i in range(2):
@@ -1801,7 +1851,7 @@
       # Ensure that some refs exist.  Otherwise, we probably aren't looking
       # at a real git repository and may have a bad url.
       if not self.bare_ref.all:
-          ok = False
+        ok = False
 
       if alt_dir:
         if old_packed != '':
@@ -2147,7 +2197,7 @@
     symlink_dirs = ['hooks', 'objects', 'rr-cache', 'svn']
     if share_refs:
       # These objects can only be used by a single working tree.
-      symlink_files += ['config', 'packed-refs']
+      symlink_files += ['config', 'packed-refs', 'shallow']
       symlink_dirs += ['logs', 'refs']
     to_symlink = symlink_files + symlink_dirs
 
@@ -2167,6 +2217,14 @@
         if name in symlink_dirs and not os.path.lexists(src):
           os.makedirs(src)
 
+        # If the source file doesn't exist, ensure the destination
+        # file doesn't either.
+        if name in symlink_files and not os.path.lexists(src):
+          try:
+            os.remove(dst)
+          except OSError:
+            pass
+
         if name in to_symlink:
           os.symlink(os.path.relpath(src, os.path.dirname(dst)), dst)
         elif copy_all and not os.path.islink(dst):
@@ -2195,7 +2253,7 @@
       if GitCommand(self, cmd).Wait() != 0:
         raise GitError("cannot initialize work tree")
 
-      self._CopyFiles()
+      self._CopyAndLinkFiles()
 
   def _gitdir_path(self, path):
     return os.path.realpath(os.path.join(self.gitdir, path))
@@ -2287,8 +2345,8 @@
           out = iter(out[:-1].split('\0'))  # pylint: disable=W1401
           while out:
             try:
-              info = out.next()
-              path = out.next()
+              info = next(out)
+              path = next(out)
             except StopIteration:
               break
 
@@ -2314,7 +2372,7 @@
             info = _Info(path, *info)
             if info.status in ('R', 'C'):
               info.src_path = info.path
-              info.path = out.next()
+              info.path = next(out)
             r[info.path] = info
         return r
       finally:
@@ -2327,8 +2385,8 @@
         path = os.path.join(self._project.worktree, '.git', HEAD)
       try:
         fd = open(path, 'rb')
-      except IOError:
-        raise NoManifestException(path)
+      except IOError as e:
+        raise NoManifestException(path, str(e))
       try:
         line = fd.read()
       finally:
diff --git a/repo b/repo
index 768f11f..3fd0166 100755
--- a/repo
+++ b/repo
@@ -114,6 +114,7 @@
 import optparse
 import os
 import re
+import shutil
 import stat
 import subprocess
 import sys
@@ -138,10 +139,6 @@
 
 # Python version check
 ver = sys.version_info
-if ver[0] == 3:
-  _print('warning: Python 3 support is currently experimental. YMMV.\n'
-         'Please use Python 2.6 - 2.7 instead.',
-         file=sys.stderr)
 if (ver[0], ver[1]) < MIN_PYTHON_VERSION:
   _print('error: Python version %s unsupported.\n'
          'Please use Python 2.6 - 2.7 instead.'
@@ -741,12 +738,7 @@
       try:
         _Init(args)
       except CloneFailure:
-        for root, dirs, files in os.walk(repodir, topdown=False):
-          for name in files:
-            os.remove(os.path.join(root, name))
-          for name in dirs:
-            os.rmdir(os.path.join(root, name))
-        os.rmdir(repodir)
+        shutil.rmtree(repodir, ignore_errors=True)
         sys.exit(1)
       repo_main, rel_repo_dir = _FindRepo()
     else:
@@ -772,4 +764,8 @@
 
 
 if __name__ == '__main__':
+  if ver[0] == 3:
+    _print('warning: Python 3 support is currently experimental. YMMV.\n'
+           'Please use Python 2.6 - 2.7 instead.',
+           file=sys.stderr)
   main(sys.argv[1:])
diff --git a/subcmds/forall.py b/subcmds/forall.py
index e2a420a..7771ec1 100644
--- a/subcmds/forall.py
+++ b/subcmds/forall.py
@@ -14,7 +14,9 @@
 # limitations under the License.
 
 from __future__ import print_function
+import errno
 import fcntl
+import multiprocessing
 import re
 import os
 import select
@@ -31,6 +33,7 @@
   'log',
 ]
 
+
 class ForallColoring(Coloring):
   def __init__(self, config):
     Coloring.__init__(self, config, 'forall')
@@ -87,6 +90,12 @@
 REPO_RREV is the name of the revision from the manifest, exactly
 as written in the manifest.
 
+REPO_COUNT is the total number of projects being iterated.
+
+REPO_I is the current (1-based) iteration count. Can be used in
+conjunction with REPO_COUNT to add a simple progress indicator to your
+command.
+
 REPO__* are any extra environment variables, specified by the
 "annotation" element under any project element.  This can be useful
 for differentiating trees based on user-specific criteria, or simply
@@ -126,9 +135,31 @@
     g.add_option('-v', '--verbose',
                  dest='verbose', action='store_true',
                  help='Show command error messages')
+    g.add_option('-j', '--jobs',
+                 dest='jobs', action='store', type='int', default=1,
+                 help='number of commands to execute simultaneously')
 
   def WantPager(self, opt):
-    return opt.project_header
+    return opt.project_header and opt.jobs == 1
+
+  def _SerializeProject(self, project):
+    """ Serialize a project._GitGetByExec instance.
+
+    project._GitGetByExec is not pickle-able. Instead of trying to pass it
+    around between processes, make a dict ourselves containing only the
+    attributes that we need.
+
+    """
+    return {
+      'name': project.name,
+      'relpath': project.relpath,
+      'remote_name': project.remote.name,
+      'lrev': project.GetRevisionId(),
+      'rrev': project.revisionExpr,
+      'annotations': dict((a.name, a.value) for a in project.annotations),
+      'gitdir': project.gitdir,
+      'worktree': project.worktree,
+    }
 
   def Execute(self, opt, args):
     if not opt.command:
@@ -167,123 +198,165 @@
       # pylint: enable=W0631
 
     mirror = self.manifest.IsMirror
-    out = ForallColoring(self.manifest.manifestProject.config)
-    out.redirect(sys.stdout)
-
     rc = 0
-    first = True
 
     if not opt.regex:
       projects = self.GetProjects(args)
     else:
       projects = self.FindProjects(args)
 
-    for project in projects:
-      env = os.environ.copy()
-      def setenv(name, val):
-        if val is None:
-          val = ''
-        env[name] = val.encode()
+    os.environ['REPO_COUNT'] = str(len(projects))
 
-      setenv('REPO_PROJECT', project.name)
-      setenv('REPO_PATH', project.relpath)
-      setenv('REPO_REMOTE', project.remote.name)
-      setenv('REPO_LREV', project.GetRevisionId())
-      setenv('REPO_RREV', project.revisionExpr)
-      for a in project.annotations:
-        setenv("REPO__%s" % (a.name), a.value)
-
-      if mirror:
-        setenv('GIT_DIR', project.gitdir)
-        cwd = project.gitdir
-      else:
-        cwd = project.worktree
-
-      if not os.path.exists(cwd):
-        if (opt.project_header and opt.verbose) \
-        or not opt.project_header:
-          print('skipping %s/' % project.relpath, file=sys.stderr)
-        continue
-
-      if opt.project_header:
-        stdin = subprocess.PIPE
-        stdout = subprocess.PIPE
-        stderr = subprocess.PIPE
-      else:
-        stdin = None
-        stdout = None
-        stderr = None
-
-      p = subprocess.Popen(cmd,
-                           cwd = cwd,
-                           shell = shell,
-                           env = env,
-                           stdin = stdin,
-                           stdout = stdout,
-                           stderr = stderr)
-
-      if opt.project_header:
-        class sfd(object):
-          def __init__(self, fd, dest):
-            self.fd = fd
-            self.dest = dest
-          def fileno(self):
-            return self.fd.fileno()
-
-        empty = True
-        errbuf = ''
-
-        p.stdin.close()
-        s_in = [sfd(p.stdout, sys.stdout),
-                sfd(p.stderr, sys.stderr)]
-
-        for s in s_in:
-          flags = fcntl.fcntl(s.fd, fcntl.F_GETFL)
-          fcntl.fcntl(s.fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)
-
-        while s_in:
-          in_ready, _out_ready, _err_ready = select.select(s_in, [], [])
-          for s in in_ready:
-            buf = s.fd.read(4096)
-            if not buf:
-              s.fd.close()
-              s_in.remove(s)
-              continue
-
-            if not opt.verbose:
-              if s.fd != p.stdout:
-                errbuf += buf
-                continue
-
-            if empty:
-              if first:
-                first = False
-              else:
-                out.nl()
-
-              if mirror:
-                project_header_path = project.name
-              else:
-                project_header_path = project.relpath
-              out.project('project %s/', project_header_path)
-              out.nl()
-              out.flush()
-              if errbuf:
-                sys.stderr.write(errbuf)
-                sys.stderr.flush()
-                errbuf = ''
-              empty = False
-
-            s.dest.write(buf)
-            s.dest.flush()
-
-      r = p.wait()
-      if r != 0:
-        if r != rc:
-          rc = r
-        if opt.abort_on_errors:
-          print("error: %s: Aborting due to previous error" % project.relpath,
-                file=sys.stderr)
-          sys.exit(r)
+    pool = multiprocessing.Pool(opt.jobs)
+    try:
+      config = self.manifest.manifestProject.config
+      results_it = pool.imap(
+         DoWorkWrapper,
+         [[mirror, opt, cmd, shell, cnt, config, self._SerializeProject(p)]
+          for cnt, p in enumerate(projects)]
+      )
+      pool.close()
+      for r in results_it:
+        rc = rc or r
+        if r != 0 and opt.abort_on_errors:
+          raise Exception('Aborting due to previous error')
+    except (KeyboardInterrupt, WorkerKeyboardInterrupt):
+      # Catch KeyboardInterrupt raised inside and outside of workers
+      print('Interrupted - terminating the pool')
+      pool.terminate()
+      rc = rc or errno.EINTR
+    except Exception as e:
+      # Catch any other exceptions raised
+      print('Got an error, terminating the pool: %r' % e,
+            file=sys.stderr)
+      pool.terminate()
+      rc = rc or getattr(e, 'errno', 1)
+    finally:
+      pool.join()
     if rc != 0:
       sys.exit(rc)
+
+
+class WorkerKeyboardInterrupt(Exception):
+  """ Keyboard interrupt exception for worker processes. """
+  pass
+
+
+def DoWorkWrapper(args):
+  """ A wrapper around the DoWork() method.
+
+  Catch the KeyboardInterrupt exceptions here and re-raise them as a different,
+  ``Exception``-based exception to stop it flooding the console with stacktraces
+  and making the parent hang indefinitely.
+
+  """
+  project = args.pop()
+  try:
+    return DoWork(project, *args)
+  except KeyboardInterrupt:
+    print('%s: Worker interrupted' % project['name'])
+    raise WorkerKeyboardInterrupt()
+
+
+def DoWork(project, mirror, opt, cmd, shell, cnt, config):
+  env = os.environ.copy()
+  def setenv(name, val):
+    if val is None:
+      val = ''
+    env[name] = val.encode()
+
+  setenv('REPO_PROJECT', project['name'])
+  setenv('REPO_PATH', project['relpath'])
+  setenv('REPO_REMOTE', project['remote_name'])
+  setenv('REPO_LREV', project['lrev'])
+  setenv('REPO_RREV', project['rrev'])
+  setenv('REPO_I', str(cnt + 1))
+  for name in project['annotations']:
+    setenv("REPO__%s" % (name), project['annotations'][name])
+
+  if mirror:
+    setenv('GIT_DIR', project['gitdir'])
+    cwd = project['gitdir']
+  else:
+    cwd = project['worktree']
+
+  if not os.path.exists(cwd):
+    if (opt.project_header and opt.verbose) \
+    or not opt.project_header:
+      print('skipping %s/' % project['relpath'], file=sys.stderr)
+    return
+
+  if opt.project_header:
+    stdin = subprocess.PIPE
+    stdout = subprocess.PIPE
+    stderr = subprocess.PIPE
+  else:
+    stdin = None
+    stdout = None
+    stderr = None
+
+  p = subprocess.Popen(cmd,
+                       cwd=cwd,
+                       shell=shell,
+                       env=env,
+                       stdin=stdin,
+                       stdout=stdout,
+                       stderr=stderr)
+
+  if opt.project_header:
+    out = ForallColoring(config)
+    out.redirect(sys.stdout)
+    class sfd(object):
+      def __init__(self, fd, dest):
+        self.fd = fd
+        self.dest = dest
+      def fileno(self):
+        return self.fd.fileno()
+
+    empty = True
+    errbuf = ''
+
+    p.stdin.close()
+    s_in = [sfd(p.stdout, sys.stdout),
+            sfd(p.stderr, sys.stderr)]
+
+    for s in s_in:
+      flags = fcntl.fcntl(s.fd, fcntl.F_GETFL)
+      fcntl.fcntl(s.fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)
+
+    while s_in:
+      in_ready, _out_ready, _err_ready = select.select(s_in, [], [])
+      for s in in_ready:
+        buf = s.fd.read(4096)
+        if not buf:
+          s.fd.close()
+          s_in.remove(s)
+          continue
+
+        if not opt.verbose:
+          if s.fd != p.stdout:
+            errbuf += buf
+            continue
+
+        if empty and out:
+          if not cnt == 0:
+            out.nl()
+
+          if mirror:
+            project_header_path = project['name']
+          else:
+            project_header_path = project['relpath']
+          out.project('project %s/', project_header_path)
+          out.nl()
+          out.flush()
+          if errbuf:
+            sys.stderr.write(errbuf)
+            sys.stderr.flush()
+            errbuf = ''
+          empty = False
+
+        s.dest.write(buf)
+        s.dest.flush()
+
+  r = p.wait()
+  return r
diff --git a/subcmds/status.py b/subcmds/status.py
index 41c4429..b42675e 100644
--- a/subcmds/status.py
+++ b/subcmds/status.py
@@ -113,7 +113,7 @@
     try:
       state = project.PrintWorkTreeStatus(output)
       if state == 'CLEAN':
-        clean_counter.next()
+        next(clean_counter)
     finally:
       sem.release()
 
@@ -141,7 +141,7 @@
       for project in all_projects:
         state = project.PrintWorkTreeStatus()
         if state == 'CLEAN':
-          counter.next()
+          next(counter)
     else:
       sem = _threading.Semaphore(opt.jobs)
       threads_and_output = []
@@ -164,7 +164,7 @@
         t.join()
         output.dump(sys.stdout)
         output.close()
-    if len(all_projects) == counter.next():
+    if len(all_projects) == next(counter):
       print('nothing to commit (working directory clean)')
 
     if opt.orphans:
diff --git a/subcmds/sync.py b/subcmds/sync.py
index a0a6896..6f77310 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -14,10 +14,10 @@
 # limitations under the License.
 
 from __future__ import print_function
+import json
 import netrc
 from optparse import SUPPRESS_HELP
 import os
-import pickle
 import re
 import shutil
 import socket
@@ -760,7 +760,7 @@
   _ALPHA = 0.5
 
   def __init__(self, manifest):
-    self._path = os.path.join(manifest.repodir, '.repopickle_fetchtimes')
+    self._path = os.path.join(manifest.repodir, '.repo_fetchtimes.json')
     self._times = None
     self._seen = set()
 
@@ -779,22 +779,17 @@
   def _Load(self):
     if self._times is None:
       try:
-        f = open(self._path, 'rb')
-      except IOError:
-        self._times = {}
-        return self._times
-      try:
+        f = open(self._path)
         try:
-          self._times = pickle.load(f)
-        except IOError:
-          try:
-            os.remove(self._path)
-          except OSError:
-            pass
-          self._times = {}
-      finally:
-        f.close()
-    return self._times
+          self._times = json.load(f)
+        finally:
+          f.close()
+      except (IOError, ValueError):
+        try:
+          os.remove(self._path)
+        except OSError:
+          pass
+        self._times = {}
 
   def Save(self):
     if self._times is None:
@@ -808,13 +803,13 @@
       del self._times[name]
 
     try:
-      f = open(self._path, 'wb')
+      f = open(self._path, 'w')
       try:
-        pickle.dump(self._times, f)
-      except (IOError, OSError, pickle.PickleError):
-        try:
-          os.remove(self._path)
-        except OSError:
-          pass
-    finally:
-      f.close()
+        json.dump(self._times, f, indent=2)
+      finally:
+        f.close()
+    except (IOError, TypeError):
+      try:
+        os.remove(self._path)
+      except OSError:
+        pass
diff --git a/subcmds/upload.py b/subcmds/upload.py
index e2fa261..0ee36df 100644
--- a/subcmds/upload.py
+++ b/subcmds/upload.py
@@ -25,10 +25,12 @@
 from project import RepoHook
 
 from pyversion import is_python3
+# pylint:disable=W0622
 if not is_python3():
-  # pylint:disable=W0622
   input = raw_input
-  # pylint:enable=W0622
+else:
+  unicode = str
+# pylint:enable=W0622
 
 UNUSUAL_COMMIT_THRESHOLD = 5