diff --git a/project.py b/project.py
index 5bead64..a5d35bf 100644
--- a/project.py
+++ b/project.py
@@ -1832,6 +1832,122 @@
                             patch_id,
                             self.bare_git.rev_parse('FETCH_HEAD'))
 
+  def DeleteWorktree(self, quiet=False, force=False):
+    """Delete the source checkout and any other housekeeping tasks.
+
+    This currently leaves behind the internal .repo/ cache state.  This helps
+    when switching branches or manifest changes get reverted as we don't have
+    to redownload all the git objects.  But we should do some GC at some point.
+
+    Args:
+      quiet: Whether to hide normal messages.
+      force: Always delete tree even if dirty.
+
+    Returns:
+      True if the worktree was completely cleaned out.
+    """
+    if self.IsDirty():
+      if force:
+        print('warning: %s: Removing dirty project: uncommitted changes lost.' %
+              (self.relpath,), file=sys.stderr)
+      else:
+        print('error: %s: Cannot remove project: uncommitted changes are '
+              'present.\n' % (self.relpath,), file=sys.stderr)
+        return False
+
+    if not quiet:
+      print('%s: Deleting obsolete checkout.' % (self.relpath,))
+
+    # Unlock and delink from the main worktree.  We don't use git's worktree
+    # remove because it will recursively delete projects -- we handle that
+    # ourselves below.  https://crbug.com/git/48
+    if self.use_git_worktrees:
+      needle = platform_utils.realpath(self.gitdir)
+      # Find the git worktree commondir under .repo/worktrees/.
+      output = self.bare_git.worktree('list', '--porcelain').splitlines()[0]
+      assert output.startswith('worktree '), output
+      commondir = output[9:]
+      # Walk each of the git worktrees to see where they point.
+      configs = os.path.join(commondir, 'worktrees')
+      for name in os.listdir(configs):
+        gitdir = os.path.join(configs, name, 'gitdir')
+        with open(gitdir) as fp:
+          relpath = fp.read().strip()
+        # Resolve the checkout path and see if it matches this project.
+        fullpath = platform_utils.realpath(os.path.join(configs, name, relpath))
+        if fullpath == needle:
+          platform_utils.rmtree(os.path.join(configs, name))
+
+    # Delete the .git directory first, so we're less likely to have a partially
+    # working git repository around. There shouldn't be any git projects here,
+    # so rmtree works.
+
+    # Try to remove plain files first in case of git worktrees.  If this fails
+    # for any reason, we'll fall back to rmtree, and that'll display errors if
+    # it can't remove things either.
+    try:
+      platform_utils.remove(self.gitdir)
+    except OSError:
+      pass
+    try:
+      platform_utils.rmtree(self.gitdir)
+    except OSError as e:
+      if e.errno != errno.ENOENT:
+        print('error: %s: %s' % (self.gitdir, e), file=sys.stderr)
+        print('error: %s: Failed to delete obsolete checkout; remove manually, '
+              'then run `repo sync -l`.' % (self.relpath,), file=sys.stderr)
+        return False
+
+    # Delete everything under the worktree, except for directories that contain
+    # another git project.
+    dirs_to_remove = []
+    failed = False
+    for root, dirs, files in platform_utils.walk(self.worktree):
+      for f in files:
+        path = os.path.join(root, f)
+        try:
+          platform_utils.remove(path)
+        except OSError as e:
+          if e.errno != errno.ENOENT:
+            print('error: %s: Failed to remove: %s' % (path, e), file=sys.stderr)
+            failed = True
+      dirs[:] = [d for d in dirs
+                 if not os.path.lexists(os.path.join(root, d, '.git'))]
+      dirs_to_remove += [os.path.join(root, d) for d in dirs
+                         if os.path.join(root, d) not in dirs_to_remove]
+    for d in reversed(dirs_to_remove):
+      if platform_utils.islink(d):
+        try:
+          platform_utils.remove(d)
+        except OSError as e:
+          if e.errno != errno.ENOENT:
+            print('error: %s: Failed to remove: %s' % (d, e), file=sys.stderr)
+            failed = True
+      elif not platform_utils.listdir(d):
+        try:
+          platform_utils.rmdir(d)
+        except OSError as e:
+          if e.errno != errno.ENOENT:
+            print('error: %s: Failed to remove: %s' % (d, e), file=sys.stderr)
+            failed = True
+    if failed:
+      print('error: %s: Failed to delete obsolete checkout.' % (self.relpath,),
+            file=sys.stderr)
+      print('       Remove manually, then run `repo sync -l`.', file=sys.stderr)
+      return False
+
+    # Try deleting parent dirs if they are empty.
+    path = self.worktree
+    while path != self.manifest.topdir:
+      try:
+        platform_utils.rmdir(path)
+      except OSError as e:
+        if e.errno != errno.ENOENT:
+          break
+      path = os.path.dirname(path)
+
+    return True
+
 # Branch Management ##
   def GetHeadPath(self):
     """Return the full path to the HEAD ref."""
diff --git a/subcmds/sync.py b/subcmds/sync.py
index eada76a..f2af0ec 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -16,7 +16,6 @@
 
 from __future__ import print_function
 
-import errno
 import json
 import netrc
 from optparse import SUPPRESS_HELP
@@ -633,74 +632,6 @@
     else:
       self.manifest._Unload()
 
-  def _DeleteProject(self, path):
-    print('Deleting obsolete path %s' % path, file=sys.stderr)
-
-    # Delete the .git directory first, so we're less likely to have a partially
-    # working git repository around. There shouldn't be any git projects here,
-    # so rmtree works.
-    dotgit = os.path.join(path, '.git')
-    # Try to remove plain files first in case of git worktrees.  If this fails
-    # for any reason, we'll fall back to rmtree, and that'll display errors if
-    # it can't remove things either.
-    try:
-      platform_utils.remove(dotgit)
-    except OSError:
-      pass
-    try:
-      platform_utils.rmtree(dotgit)
-    except OSError as e:
-      if e.errno != errno.ENOENT:
-        print('error: %s: %s' % (dotgit, str(e)), file=sys.stderr)
-        print('error: %s: Failed to delete obsolete path; remove manually, then '
-              'run sync again' % (path,), file=sys.stderr)
-        return 1
-
-    # Delete everything under the worktree, except for directories that contain
-    # another git project
-    dirs_to_remove = []
-    failed = False
-    for root, dirs, files in platform_utils.walk(path):
-      for f in files:
-        try:
-          platform_utils.remove(os.path.join(root, f))
-        except OSError as e:
-          print('Failed to remove %s (%s)' % (os.path.join(root, f), str(e)), file=sys.stderr)
-          failed = True
-      dirs[:] = [d for d in dirs
-                 if not os.path.lexists(os.path.join(root, d, '.git'))]
-      dirs_to_remove += [os.path.join(root, d) for d in dirs
-                         if os.path.join(root, d) not in dirs_to_remove]
-    for d in reversed(dirs_to_remove):
-      if platform_utils.islink(d):
-        try:
-          platform_utils.remove(d)
-        except OSError as e:
-          print('Failed to remove %s (%s)' % (os.path.join(root, d), str(e)), file=sys.stderr)
-          failed = True
-      elif len(platform_utils.listdir(d)) == 0:
-        try:
-          platform_utils.rmdir(d)
-        except OSError as e:
-          print('Failed to remove %s (%s)' % (os.path.join(root, d), str(e)), file=sys.stderr)
-          failed = True
-          continue
-    if failed:
-      print('error: Failed to delete obsolete path %s' % path, file=sys.stderr)
-      print('       remove manually, then run sync again', file=sys.stderr)
-      return 1
-
-    # Try deleting parent dirs if they are empty
-    project_dir = path
-    while project_dir != self.manifest.topdir:
-      if len(platform_utils.listdir(project_dir)) == 0:
-        platform_utils.rmdir(project_dir)
-      else:
-        break
-      project_dir = os.path.dirname(project_dir)
-
-    return 0
-
   def UpdateProjectList(self, opt):
     new_project_paths = []
     for project in self.GetProjects(None, missing_ok=True):
@@ -727,23 +658,15 @@
                 remote=RemoteSpec('origin'),
                 gitdir=gitdir,
                 objdir=gitdir,
+                use_git_worktrees=os.path.isfile(gitdir),
                 worktree=os.path.join(self.manifest.topdir, path),
                 relpath=path,
                 revisionExpr='HEAD',
                 revisionId=None,
                 groups=None)
-
-            if project.IsDirty() and opt.force_remove_dirty:
-              print('WARNING: Removing dirty project "%s": uncommitted changes '
-                    'erased' % project.relpath, file=sys.stderr)
-              self._DeleteProject(project.worktree)
-            elif project.IsDirty():
-              print('error: Cannot remove project "%s": uncommitted changes '
-                    'are present' % project.relpath, file=sys.stderr)
-              print('       commit changes, then run sync again',
-                    file=sys.stderr)
-              return 1
-            elif self._DeleteProject(project.worktree):
+            if not project.DeleteWorktree(
+                quiet=opt.quiet,
+                force=opt.force_remove_dirty):
               return 1
 
     new_project_paths.sort()