To simulate the svn cp command, it would be very useful to be
replace an arbitrary file in the current revision by an
arbitrary directory from a previous one. Modify the filemodify
command to allow that:
M 040000 <tree id> pathname
This would be most useful in combination with a facility to
print the commit ids for new revisions as they are written.
Cc: Shawn O. Pearce <spearce@spearce.org> Cc: Sverre Rabbelier <srabbelier@gmail.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>