Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 74701)
+++ Misc/NEWS	(working copy)
@@ -366,6 +366,8 @@
 Library
 -------
 
+- Issue #6856: Add a filter keyword argument to TarFile.add().
+
 - Issue #4937: plat-mac/bundlebuilder revers to non-existing version.plist
 
 - Issue #6838: Use a list to accumulate the value instead of
Index: Doc/library/tarfile.rst
===================================================================
--- Doc/library/tarfile.rst	(revision 74701)
+++ Doc/library/tarfile.rst	(working copy)
@@ -389,7 +389,7 @@
       and :meth:`close`, and also supports iteration over its lines.
 
 
-.. method:: TarFile.add(name, arcname=None, recursive=True, exclude=None)
+.. method:: TarFile.add(name, arcname=None, recursive=True, exclude=None, filter=None)
 
    Add the file *name* to the archive. *name* may be any type of file (directory,
    fifo, symbolic link, etc.). If given, *arcname* specifies an alternative name
@@ -397,12 +397,22 @@
    can be avoided by setting *recursive* to :const:`False`. If *exclude* is given
    it must be a function that takes one filename argument and returns a boolean
    value. Depending on this value the respective file is either excluded
-   (:const:`True`) or added (:const:`False`).
+   (:const:`True`) or added (:const:`False`). If *filter* is specified it must
+   be a function that takes a :class:`TarInfo` object argument and returns the
+   changed TarInfo object. If it instead returns :const:`None` the TarInfo
+   object will be excluded from the archive.
 
    .. versionchanged:: 2.6
       Added the *exclude* parameter.
 
+   .. deprecated:: 2.7
+      The *exclude* parameter is deprecated, please use the *filter* parameter
+      instead.
 
+   .. versionchanged:: 2.7
+      Added the *filter* parameter.
+
+
 .. method:: TarFile.addfile(tarinfo, fileobj=None)
 
    Add the :class:`TarInfo` object *tarinfo* to the archive. If *fileobj* is given,
@@ -653,7 +663,18 @@
            print "something else."
    tar.close()
 
+How create an archive and reset the user information::
 
+    import tarfile
+    def reset(tarinfo):
+        tarinfo.uid = tarinfo.gid = 0
+        tarinfo.uname = tarinfo.gname = "root"
+        return tarinfo
+    tar = tarfile.open("sample.tar.gz", "w:gz")
+    tar.add("foo", filter=reset)
+    tar.close()
+
+
 .. _tar-formats:
 
 Supported tar formats
Index: Lib/tarfile.py
===================================================================
--- Lib/tarfile.py	(revision 74701)
+++ Lib/tarfile.py	(working copy)
@@ -1918,13 +1918,16 @@
                     print "link to", tarinfo.linkname,
             print
 
-    def add(self, name, arcname=None, recursive=True, exclude=None):
+    def add(self, name, arcname=None, recursive=True, exclude=None, filter=None):
         """Add the file `name' to the archive. `name' may be any type of file
            (directory, fifo, symbolic link, etc.). If given, `arcname'
            specifies an alternative name for the file in the archive.
            Directories are added recursively by default. This can be avoided by
            setting `recursive' to False. `exclude' is a function that should
-           return True for each filename to be excluded.
+           return True for each filename to be excluded. `filter' is a function
+           that expects a TarInfo object as argument and allows changing it
+           before it will be added, if `filter' returns None the TarInfo will
+           be excluded from the archive.
         """
         self._check("aw")
 
@@ -1932,9 +1935,13 @@
             arcname = name
 
         # Exclude pathnames.
-        if exclude is not None and exclude(name):
-            self._dbg(2, "tarfile: Excluded %r" % name)
-            return
+        if exclude is not None:
+            import warnings
+            warnings.warn("use the format attribute instead",
+                    DeprecationWarning, 2)
+            if exclude(name):
+                self._dbg(2, "tarfile: Excluded %r" % name)
+                return
 
         # Skip if somebody tries to archive the archive...
         if self.name is not None and os.path.abspath(name) == self.name:
@@ -1950,6 +1957,13 @@
             self._dbg(1, "tarfile: Unsupported type %r" % name)
             return
 
+        # Change or exclude the TarInfo object.
+        if filter is not None:
+            tarinfo = filter(tarinfo)
+            if tarinfo is None:
+                self._dbg(2, "tarfile: Excluded %r" % name)
+                return
+
         # Append the tar header and data to the archive.
         if tarinfo.isreg():
             f = bltn_open(name, "rb")
@@ -1960,7 +1974,7 @@
             self.addfile(tarinfo)
             if recursive:
                 for f in os.listdir(name):
-                    self.add(os.path.join(name, f), os.path.join(arcname, f), recursive, exclude)
+                    self.add(os.path.join(name, f), os.path.join(arcname, f), recursive, exclude, filter)
 
         else:
             self.addfile(tarinfo)
Index: Lib/test/test_tarfile.py
===================================================================
--- Lib/test/test_tarfile.py	(revision 74701)
+++ Lib/test/test_tarfile.py	(working copy)
@@ -660,6 +660,34 @@
         finally:
             shutil.rmtree(tempdir)
 
+    def test_filter(self):
+        tempdir = os.path.join(TEMPDIR, "filter")
+        os.mkdir(tempdir)
+        try:
+            for name in ("foo", "bar", "baz"):
+                name = os.path.join(tempdir, name)
+                open(name, "wb").close()
+
+            def filter(tarinfo):
+                if os.path.basename(tarinfo.name) == "bar":
+                    return
+                tarinfo.uid = 123
+                tarinfo.uname = "foo"
+                return tarinfo
+
+            tar = tarfile.open(tmpname, self.mode, encoding="iso8859-1")
+            tar.add(tempdir, arcname="empty_dir", filter=filter)
+            tar.close()
+
+            tar = tarfile.open(tmpname, "r")
+            for tarinfo in tar:
+                self.assertEqual(tarinfo.uid, 123)
+                self.assertEqual(tarinfo.uname, "foo")
+            self.assertEqual(len(tar.getmembers()), 3)
+            tar.close()
+        finally:
+            shutil.rmtree(tempdir)
+
     # Guarantee that stored pathnames are not modified. Don't
     # remove ./ or ../ or double slashes. Still make absolute
     # pathnames relative.