With git-filter-branch --subdirectory-filter <subdirectory> you can
get at the history, as seen by a certain subdirectory. The history
of the rewritten branch will only contain commits that touched that
subdirectory, and the subdirectory will be rewritten to be the new
project root.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>