During Vim editing, We must have to delete unnecessary trailing whitespace which make code easy to read or merge.

So you can add .vimrc file in /YOUR_HOME_PATH/

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$ cd
$ vim .vimrc

Add below contents then save and exit.

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hi Whitespace ctermbg=darkred guibg=darkcyan
autocmd BufEnter * if &ft != 'help' | match Whitespace /\s\+$/ | endif
autocmd BufEnter * if &ft == 'help' | match none /\s\+$/ | endif

Enjoy it.

Reference : vim 顯示多餘空白( trailing whitespace )