feat(magit): introduce +magit-auto-revert option

Provides more control over our auto-reverting feature, and changes its
behavior to only target non-remote buffers by default, because reverting
remote buffers could be tremendously slow.

This could be later improved to treat TRAMP buffers with local
methods (like sudo) as local buffers.

Fix: #8354

modules/tools/magit/config.el

@@ -12,6 +12,28 @@ left and right fringe.
 
 Only has an effect in GUI Emacs.")
 
+(defvar +magit-auto-revert 'local
+  "If non-nil, revert associated buffers after Git operations with side-effects.
+
+These buffers are auto-reverted immediately if they're visible or reverted next
+time they're switched to. This is intended to be a much more efficient
+replacement for `magit-auto-revert-mode' and `global-auto-revert-mode', and
+should not be used together with them! Set this to `nil' if you plan to use the
+above.
+
+Accepts one of three values OR a predicate function:
+
+t
+  Revert any associated buffers.
+local
+  Same as `t', except remote (TRAMP) buffers are ignored.
+nil
+  Don't do any auto-reverting at all.
+FUNCTION
+  If given a function, it will be passed a buffer associated with the current
+  Magit session and must return non-nil to signal this is buffer is safe to
+  revert (now or later, when switched to).")
+
 
 ;;
 ;;; Packages