Revert feature added in bfd96e995d using project directories in vc (bug#41821)

etc/NEWS

@@ -197,10 +197,6 @@ The relevant commands are those that don't change the VC state.
 The non-file buffers which can use VC commands are those that have
 their 'default-directory' under VC.
 
-*** 'M-n' now works in minibuffer prompts of VC commands.
-Typing 'M-n' in the minibuffer that prompts for a VC directory in VC
-commands now retrieves directories of previously used VC projects.
-
 *** New command 'vc-dir-root' uses the root directory without asking.
 
 *** New commands 'vc-dir-mark-registered-files' (bound to '* r') and

lisp/vc/vc-dir.el

@@ -1366,7 +1366,7 @@ These are the commands available for use in the file status buffer:
     ;; Otherwise if you do C-x v d -> C-x C-f -> C-x v d
     ;; you may get a new *vc-dir* buffer, different from the original
     (file-truename (read-directory-name "VC status for directory: "
-					(vc-root-dir) (vc-known-roots) t
+					(vc-root-dir) nil t
 					nil))
     (if current-prefix-arg
 	(intern

lisp/vc/vc-hooks.el

@@ -299,11 +299,6 @@ non-nil if FILE exists and its contents were successfully inserted."
     (set-buffer-modified-p nil)
     t))
 
-(declare-function project-try-vc "project")
-(defun vc-known-roots ()
-  "Return a list of known vc roots."
-  (seq-filter #'project-try-vc (project-known-project-roots)))
-
 (defun vc-find-root (file witness)
   "Find the root of a checked out project.
 The function walks up the directory tree from FILE looking for WITNESS.

lisp/vc/vc.el

@@ -2001,8 +2001,7 @@ saving the buffer."
 	  rootdir working-revision)
       (if backend
 	  (setq rootdir (vc-call-backend backend 'root default-directory))
-	(setq rootdir (read-directory-name "Directory for VC root-diff: "
-                                           nil (vc-known-roots)))
+	(setq rootdir (read-directory-name "Directory for VC root-diff: "))
 	(setq backend (vc-responsible-backend rootdir))
 	(if backend
 	    (setq default-directory rootdir)
@@ -2546,8 +2545,7 @@ with its diffs (if the underlying VCS supports that)."
 	 rootdir)
     (if backend
 	(setq rootdir (vc-call-backend backend 'root default-directory))
-      (setq rootdir (read-directory-name "Directory for VC revision log: "
-                                         nil (vc-known-roots)))
+      (setq rootdir (read-directory-name "Directory for VC revision log: "))
       (setq backend (vc-responsible-backend rootdir))
       (unless backend
         (error "Directory is not version controlled")))