Some comments on the patch:

+   The buffer size value which will be used to read the file contents. Defaults
+   to 8192 bytes.

I would consider including the units for the value here (e.g. "The buffer
size value in bytes...").

+   When *shallow* flag is set to False, :data:`filecmp.BUFSIZE` bytes of file
+   content will be read and compared.

Should this instead read something like, "When the *shallow* flag is set to
False, the file contents will be read and compared, reading
:data:`filecmp.BUFSIZE` bytes at a time."  The current wording suggests
that only the first BUFSIZE bytes will be looked at.

+   The :class:`dircmp` class compares files by doing *shallow* comparisons as
+   described for :func:`filecmp.cmp`.

This change was already committed as part of issue 15250.

+   The :class:`dircmp` class offers a number of interesting attributes that may
+   be used to get various bits of information about the directory trees being

This change was already committed as part of issue 15250.

    .. attribute:: common_dirs

-      Subdirectories in both *a* and *b*.
+      Subdirectories in both *dir1* and *dir2*, using the class's file
+      comparison operator.

The phrase "using the class's file comparison operator" should not be added
to common_dirs.  common_dirs does not look at file contents.

    .. attribute:: common_files

-      Files in both *a* and *b*
+      Files in both *dir1* and *dir2*, whose contents differ according to the
+      class's file comparison operator.

The phrase "whose contents differ according to the class's file comparison
operator" should not be added to common_files.  common_files does not look
at file contents.

    .. attribute:: same_files

-      Files which are identical in both *a* and *b*.
+      Files which are identical in both *dir1* and *dir2*.

This line should reflect the change committed for issue 15250.

    .. attribute:: diff_files

-      Files which are in both *a* and *b*, whose contents differ.
+      Files which are in both *dir1* and *dir2*, whose contents differ.

This line should reflect the change committed for issue 15250.