diff --git a/subcmds/compute_snapshot_check.py b/subcmds/compute_snapshot_check.py
new file mode 100644
index 0000000..82db359
--- /dev/null
+++ b/subcmds/compute_snapshot_check.py
@@ -0,0 +1,169 @@
+#
+# Copyright (C) 2008 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import sys
+import tempfile
+
+from command import Command
+from error import GitError, NoSuchProjectError
+from git_config import IsId
+from import_tar import ImportTar
+from import_zip import ImportZip
+from project import Project
+from remote import Remote
+
+def _ToCommit(project, rev):
+  return project.bare_git.rev_parse('--verify', '%s^0' % rev)
+
+def _Missing(project, rev):
+  return project._revlist('--objects', rev, '--not', '--all')
+
+
+class ComputeSnapshotCheck(Command):
+  common = False
+  helpSummary = "Compute the check value for a new snapshot"
+  helpUsage = """
+%prog -p NAME -v VERSION -s FILE [options]
+"""
+  helpDescription = """
+%prog computes and then displays the proper check value for a
+snapshot, so it can be pasted into the manifest file for a project.
+"""
+
+  def _Options(self, p):
+    g = p.add_option_group('Snapshot description options')
+    g.add_option('-p', '--project',
+                 dest='project', metavar='NAME',
+                 help='destination project name')
+    g.add_option('-v', '--version',
+                 dest='version', metavar='VERSION',
+                 help='upstream version/revision identifier')
+    g.add_option('-s', '--snapshot',
+                 dest='snapshot', metavar='PATH',
+                 help='local tarball path')
+    g.add_option('--new-project',
+                 dest='new_project', action='store_true',
+                 help='destinition is a new project')
+    g.add_option('--keep',
+                 dest='keep_git', action='store_true',
+                 help='keep the temporary git repository')
+
+    g = p.add_option_group('Base revision grafting options')
+    g.add_option('--prior',
+                 dest='prior', metavar='COMMIT',
+                 help='prior revision checksum')
+
+    g = p.add_option_group('Path mangling options')
+    g.add_option('--strip-prefix',
+                 dest='strip_prefix', metavar='PREFIX',
+                 help='remove prefix from all paths on import')
+    g.add_option('--insert-prefix',
+                 dest='insert_prefix', metavar='PREFIX',
+                 help='insert prefix before all paths on import')
+
+
+  def _Compute(self, opt):
+    try:
+      real_project = self.GetProjects([opt.project])[0]
+    except NoSuchProjectError:
+      if opt.new_project:
+        print >>sys.stderr, \
+          "warning: project '%s' does not exist" % opt.project
+      else:
+        raise NoSuchProjectError(opt.project)
+
+    self._tmpdir = tempfile.mkdtemp()
+    project = Project(manifest = self.manifest,
+                      name = opt.project,
+                      remote = Remote('origin'),
+                      gitdir = os.path.join(self._tmpdir, '.git'),
+                      worktree = self._tmpdir,
+                      relpath = opt.project,
+                      revision = 'refs/heads/master')
+    project._InitGitDir()
+
+    url = 'file://%s' % os.path.abspath(opt.snapshot)
+
+    imp = None
+    for cls in [ImportTar, ImportZip]:
+      if cls.CanAccept(url):
+        imp = cls()
+        break
+    if not imp:
+      print >>sys.stderr, 'error: %s unsupported' % opt.snapshot
+      sys.exit(1)
+
+    imp.SetProject(project)
+    imp.SetVersion(opt.version)
+    imp.AddUrl(url)
+
+    if opt.prior:
+      if opt.new_project:
+        if not IsId(opt.prior):
+          print >>sys.stderr, 'error: --prior=%s not valid' % opt.prior
+          sys.exit(1)
+      else:
+        try:
+          opt.prior = _ToCommit(real_project, opt.prior)
+          missing = _Missing(real_project, opt.prior)
+        except GitError, e:
+          print >>sys.stderr,\
+            'error: --prior=%s not valid\n%s' \
+            % (opt.prior, e)
+          sys.exit(1)
+        if missing:
+          print >>sys.stderr,\
+            'error: --prior=%s is valid, but is not reachable' \
+            % opt.prior
+          sys.exit(1)
+      imp.SetParent(opt.prior)
+
+    src = opt.strip_prefix
+    dst = opt.insert_prefix
+    if src or dst:
+      if src is None:
+        src = ''
+      if dst is None:
+        dst = ''
+      imp.RemapPath(src, dst)
+    commitId = imp.Import()
+
+    print >>sys.stderr,"%s\t%s" % (commitId, imp.version)
+    return project
+
+  def Execute(self, opt, args):
+    if args \
+       or not opt.project \
+       or not opt.version \
+       or not opt.snapshot:
+      self.Usage()
+
+    success = False
+    project = None
+    try:
+      self._tmpdir = None
+      project = self._Compute(opt)
+    finally:
+      if project and opt.keep_git:
+        print 'GIT_DIR = %s' % (project.gitdir)
+      elif self._tmpdir:
+        for root, dirs, files in os.walk(self._tmpdir, 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(self._tmpdir)
+