** When you visit a file that changes frequently outside Emacs--for
example, a log of output from a process that continues to run--it may be useful for Emacs to revert the file without querying you whenever you visit the file afresh with C-x C-f.

You can request this behavior for certain files by setting the variable revert-without-query to a list of regular expressions. If a file's name matches any of these regular expressions, find-file and revert-buffer revert the buffer without asking for permission--but only if you have not edited the buffer text yourself.