This adds the 'core.excludesfile' configuration variable. This variable can
hold a path to a file containing patterns of file names to exclude from
git-add, like $GIT_DIR/info/exclude. Patterns in the excludes file are used
in addition to those in info/exclude.
Signed-off-by: James Bowes <jbowes@dangerouslyinc.com> Signed-off-by: Junio C Hamano <junkio@cox.net>