How to expand tab into spaces in vi / vim
It is always good to use spaces instead of tab when editing program's source code.
In you ~/.vimrc, add the following lines
: set expandtab : set shiftwidth=4 : set softtabstop=4 : set tabstop=4
Only expandtab is needed in fact, but most opensource projects tend to maintain a consistency of 4-spaces-indent, follow it anyway.