diff --git a/hgext/largefiles/lfutil.py b/hgext/largefiles/lfutil.py
--- a/hgext/largefiles/lfutil.py
+++ b/hgext/largefiles/lfutil.py
@@ -162,6 +162,9 @@
     def __getitem__(self, key):
         return super(largefilesdirstate, self).__getitem__(unixpath(key))
 
+    def set_tracked(self, f):
+        return super(largefilesdirstate, self).set_tracked(unixpath(f))
+
     def normal(self, f):
         return super(largefilesdirstate, self).normal(unixpath(f))
 
diff --git a/hgext/narrow/narrowdirstate.py b/hgext/narrow/narrowdirstate.py
--- a/hgext/narrow/narrowdirstate.py
+++ b/hgext/narrow/narrowdirstate.py
@@ -38,6 +38,10 @@
             return super(narrowdirstate, self).normal(*args, **kwargs)
 
         @_editfunc
+        def set_tracked(self, *args):
+            return super(narrowdirstate, self).set_tracked(*args)
+
+        @_editfunc
         def add(self, *args):
             return super(narrowdirstate, self).add(*args)
 
diff --git a/hgext/sparse.py b/hgext/sparse.py
--- a/hgext/sparse.py
+++ b/hgext/sparse.py
@@ -256,6 +256,7 @@
     # Prevent adding files that are outside the sparse checkout
     editfuncs = [
         b'normal',
+        b'set_tracked',
         b'add',
         b'normallookup',
         b'copy',
diff --git a/mercurial/dirstate.py b/mercurial/dirstate.py
--- a/mercurial/dirstate.py
+++ b/mercurial/dirstate.py
@@ -83,6 +83,17 @@
     return wrap
 
 
+def requires_no_parents_change(func):
+    def wrap(self, *args, **kwargs):
+        if not self.pendingparentchange():
+            msg = 'calling `%s` inside of a parentchange context'
+            msg %= func.__name__
+            raise error.ProgrammingError(msg)
+        return func(self, *args, **kwargs)
+
+    return wrap
+
+
 @interfaceutil.implementer(intdirstate.idirstate)
 class dirstate(object):
     def __init__(
@@ -451,6 +462,24 @@
     def copies(self):
         return self._map.copymap
 
+    @requires_no_parents_change
+    def set_tracked(self, filename):
+        """a "public" method for generic code to mark a file as tracked
+
+        This function is to be called outside of "update/merge" case. For
+        example by a command like `hg add X`.
+
+        return True the file was previously untracked, False otherwise.
+        """
+        entry = self._map.get(filename)
+        if entry is None:
+            self._add(filename)
+            return True
+        elif not entry.tracked:
+            self.normallookup(filename)
+            return True
+        return False
+
     @requires_parents_change
     def update_file_reference(
         self,