add changed files from the working directory to the staging area

EXAMPLES
	git add file.x
		add file.x to the staging area
	git add -A
		add all changed and untracked files to the staging area
	git add -p file.x
		interactively add patches in file.x to the staging area (file.x has to already be tracked)
	git add -i
		start an interactive add session for adding/reverting/patching

FLAGS
	-A	all changed and untracked files
	-p	patching (interactive adding of parts of a file)
	-i	interactive add session
	-N	add an untracked file to be tracked (e.g. if you then want to run -p on that file)
