vi customization
Ubuntu and Debian use a default /usr/share/vim/vim81/defaults.vim to set the defaults.
Strangely, the setting will be destroyed when we create a file ~/.vimrc. This is very unfortunately very confusing.
The default autoindent when editing a LaTeX file is quite annoying, e.g. { of \frac{ is hit, etc.
Even after reading some posts in stackexchange I tweaked :set indent but that did not work).
I find it easier to have a full control of the behaviors of vi by editing /etc/vim/vimrc.
These are the changes I made in /etc/vim/vimrc:
(1) To avoid loading the weird /usr/share/vim/vim81/defaults.vim we shall set
let g:skip_defaults_vim = 1
(2) Turn syntax on:
if has("syntax")
syntax on
endif
(3) To remember the position of the cursor:
au BufReadPost * if line("'\"") > 1 && line("'\"") <= line("$") | exe "normal! g'\"" | endif
(4) To have a normal behavior of the mouse:
set mouse=r
Note: This link tells us how to find the cryptic variable VIMRUNTIME!
If we really want to print this value, then launch vi, then :echo $VIMRUNTIME shows the cryptic variable.