Bring back the project--value-in-dir logic

Essentialy revert commit 2389158a31, restoring the changes
and fixing the conflicts.  Motivated by the problem brought up in
bug#59722 (behavior of project-find-files/regexp when switching
projects).  We should find other ways to improve performance.

* lisp/progmodes/project.el
(project--value-in-dir, project--vc-merge-submodules-p): Restore.
(project-try-vc, project-files, project--vc-list-files)
(project-ignores, project-buffers): Use.

* test/lisp/progmodes/project-tests.el
(project-vc-supports-project-in-different-dir): New test.

* test/lisp/progmodes/project-resources/.dir-locals.el:
* test/lisp/progmodes/project-resources/foo:
* test/lisp/progmodes/project-resources/etc: New files.

lisp/progmodes/project.el

@@ -515,7 +515,8 @@ project backend implementation of `project-external-roots'.")
              (marker-re
               (mapconcat
                (lambda (m) (format "\\(%s\\)" (wildcard-to-regexp m)))
-               (append backend-markers project-vc-extra-root-markers)
+               (append backend-markers
+                       (project--value-in-dir 'project-vc-extra-root-markers dir))
                "\\|"))
              (locate-dominating-stop-dir-regexp
               (or vc-ignore-dir-regexp locate-dominating-stop-dir-regexp))
@@ -535,7 +536,7 @@ project backend implementation of `project-external-roots'.")
              project)
         (when (and
                (eq backend 'Git)
-               project-vc-merge-submodules
+               (project--vc-merge-submodules-p root)
                (project--submodule-p root))
           (let* ((parent (file-name-directory (directory-file-name root))))
             (setq root (vc-call-backend 'Git 'root parent))))
@@ -582,7 +583,7 @@ project backend implementation of `project-external-roots'.")
 (cl-defmethod project-files ((project (head vc)) &optional dirs)
   (mapcan
    (lambda (dir)
-     (let ((ignores project-vc-ignores)
+     (let ((ignores (project--value-in-dir 'project-vc-ignores (nth 2 project)))
            (backend (cadr project)))
        (when backend
          (require (intern (concat "vc-" (downcase (symbol-name backend))))))
@@ -647,7 +648,7 @@ project backend implementation of `project-external-roots'.")
               (split-string
                (apply #'vc-git--run-command-string nil "ls-files" args)
                "\0" t)))
-       (when project-vc-merge-submodules
+       (when (project--vc-merge-submodules-p default-directory)
          ;; Unfortunately, 'ls-files --recurse-submodules' conflicts with '-o'.
          (let* ((submodules (project--git-submodules))
                 (sub-files
@@ -681,6 +682,11 @@ project backend implementation of `project-external-roots'.")
           (lambda (s) (concat default-directory s))
           (split-string (buffer-string) "\0" t)))))))
 
+(defun project--vc-merge-submodules-p (dir)
+  (project--value-in-dir
+   'project-vc-merge-submodules
+   dir))
+
 (defun project--git-submodules ()
   ;; 'git submodule foreach' is much slower.
   (condition-case nil
@@ -722,7 +728,7 @@ project backend implementation of `project-external-roots'.")
          (condition-case nil
              (vc-call-backend backend 'ignore-completion-table root)
            (vc-not-supported () nil)))))
-     project-vc-ignores
+     (project--value-in-dir 'project-vc-ignores root)
      (mapcar
       (lambda (dir)
         (concat dir "/"))
@@ -753,9 +759,16 @@ DIRS must contain directory names."
   ;; Sidestep the issue of expanded/abbreviated file names here.
   (cl-set-difference files dirs :test #'file-in-directory-p))
 
+(defun project--value-in-dir (var dir)
+  (with-temp-buffer
+    (setq default-directory dir)
+    (let ((enable-local-variables :all))
+      (hack-dir-local-variables-non-file-buffer))
+    (symbol-value var)))
+
 (cl-defmethod project-buffers ((project (head vc)))
   (let* ((root (expand-file-name (file-name-as-directory (project-root project))))
-         (modules (unless (or project-vc-merge-submodules
+         (modules (unless (or (project--vc-merge-submodules-p root)
                               (project--submodule-p root))
                     (mapcar
                      (lambda (m) (format "%s%s/" root m))

test/lisp/progmodes/project-resources/.dir-locals.el

@@ -0,0 +1 @@
+((nil . ((project-vc-ignores . ("etc")))))

test/lisp/progmodes/project-resources/etc

@@ -0,0 +1 @@
+etc

test/lisp/progmodes/project-resources/foo

@@ -0,0 +1 @@
+foo

test/lisp/progmodes/project-tests.el

@@ -139,4 +139,17 @@ When `project-ignores' includes a name matching project dir."
     (should-not (null project))
     (should (string-match-p "/test/lisp/\\'" (project-root project)))))
 
+(ert-deftest project-vc-supports-project-in-different-dir ()
+  "Check that it picks up dir-locals settings from somewhere else."
+  (skip-unless (eq (vc-responsible-backend default-directory) 'Git))
+  (let* ((dir (ert-resource-directory))
+         (_ (vc-file-clearprops dir))
+         (project-vc-extra-root-markers '(".dir-locals.el"))
+         (project (project-current nil dir)))
+    (should-not (null project))
+    (should (string-match-p "/test/lisp/progmodes/project-resources/\\'" (project-root project)))
+    (should (member "etc" (project-ignores project dir)))
+    (should (equal '(".dir-locals.el" "foo")
+                   (mapcar #'file-name-nondirectory (project-files project))))))
+
 ;;; project-tests.el ends here