Add a new (empty) header file to contain the implementation for
selecting, reading, and applying pseudo-merge bitmaps.
For now this header and its corresponding implementation are left
empty, but they will evolve over the course of subsequent commit(s).
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
