* change merge and staging
always push to the top of the currently selected branch
* remove branch and sha1 from stage object #365
* REPO not longer part of GIT_PORCELAIN
SET_OBJECTS moved to private
* and remove fields from constructor
* LOG: extra ADD_* methods
Methods ADD_ERROR, ADD_INFO, and ADD_WARNING added to log class
* refactor background to use log object
refactor background to use log object instead of WRITE