Linux – How to Get the User Manual for Vim

According to the vim documentation, :q closes the current window and only quits if there are no windows left. In vim, windows are merely "viewports" where buffers can be displayed. The vim documentation itself sums this up quite nicely. From :help window:

A buffer is the in-memory text of a file.
A window is a viewport on a buffer.
A tab page is a collection of windows.

If you have the hidden option set, closing a window hides the buffer but does not "abandon" it, so vim is still keeping track of the contents. With 'hidden' set, when you "reopen" the file, you are simply re-showing/un-hiding the buffer, not actually re-opening the file on disk.

For more information take a look at

:help hidden
:help abandon

If you have vim >= 7 (I think) you can use autocmd with an event SwapExists. There you can do all from very simple things to very complicated.
Here is a simple example to put in your ~/.vimrc:

autocmd SwapExists * let v:swapchoice = "o"

If a swap file exists, this event will be triggered. The autocmd above will simply open the file in read only mode.
If v:swapchoice gets a value in an autocmd it will not prompt you what you want to do. The values you can use is listed here v:swapchoice.
For a very advanced autocmd see here: editexisting.vim
The script there can already be on your server from the installation of vim, search for editexisting.vim.