magit-get{,-all,-boolean}: improve cache

If magit--refresh-cache is activated, cache all config values at once.
Add tests for known tricky cases.

lisp/magit-git.el

@@ -1463,18 +1463,39 @@ Return a list of two integers: (A>B B>A)."
 
 ;;; Variables
 
+(defun magit-config-get-from-cached-list (key)
+  (gethash
+   ;; `git config --list' downcases first and last components of the key.
+   (--> key
+        (replace-regexp-in-string "\\`[^.]+" #'downcase it t t)
+        (replace-regexp-in-string "[^.]+\\'" #'downcase it t t))
+   (magit--with-refresh-cache (list 'config (magit-toplevel))
+     (let ((configs (make-hash-table :test 'equal)))
+       (dolist (conf (magit-git-items "config" "--list" "-z"))
+         (let* ((nl-pos (cl-position ?\n conf))
+                (key (substring conf 0 nl-pos))
+                (val (if nl-pos (substring conf (1+ nl-pos)) "")))
+           (puthash key (nconc (gethash key configs) (list val)) configs)))
+       configs))))
+
 (defun magit-get (&rest keys)
   "Return the value of Git config entry specified by KEYS."
-  (magit-git-str "config" (mapconcat 'identity keys ".")))
+  (car (last (apply 'magit-get-all keys))))
 
 (defun magit-get-all (&rest keys)
   "Return all values of the Git config entry specified by KEYS."
-  (let ((magit-git-debug nil))
-    (magit-git-items "config" "-z" "--get-all" (mapconcat 'identity keys "."))))
+  (let ((magit-git-debug nil)
+        (key (mapconcat 'identity keys ".")))
+    (if magit--refresh-cache
+        (magit-config-get-from-cached-list key)
+      (magit-git-items "config" "-z" "--get-all" key))))
 
 (defun magit-get-boolean (&rest keys)
   "Return the boolean value of Git config entry specified by KEYS."
-  (magit-git-true "config" "--bool" (mapconcat 'identity keys ".")))
+  (let ((key (mapconcat 'identity keys ".")))
+    (if magit--refresh-cache
+        (equal "true" (car (magit-config-get-from-cached-list key)))
+      (magit-git-true "config" "--bool" key))))
 
 (defun magit-set (val &rest keys)
   "Set Git config settings specified by KEYS to VAL."

t/magit-tests.el

@@ -136,6 +136,37 @@
   (should (equal (magit-toplevel   "wrap/subsubdir-link")
                  (expand-file-name "repo/"))))
 
+(defun magit-test-magit-get ()
+  (should (equal (magit-get-all "a.b") '("val1" "val2")))
+  (should (equal (magit-get "a.b") "val2"))
+  (let ((default-directory (expand-file-name "../remote/")))
+    (should (equal (magit-get "a.b") "remote-value")))
+  (should (equal (magit-get "CAM.El.Case.VAR") "value"))
+  (should (equal (magit-get "a.b2") "line1\nline2")))
+
+(ert-deftest magit-get ()
+  (magit-with-test-directory
+   (magit-git "init" "remote")
+   (let ((default-directory (expand-file-name "remote/")))
+     (magit-git "commit" "-m" "init" "--allow-empty")
+     (magit-git "config" "a.b" "remote-value"))
+   (magit-git "init" "super")
+   (setq default-directory (expand-file-name "super/"))
+   ;; Some tricky cases:
+   ;; Multiple config values.
+   (magit-git "config" "a.b" "val1")
+   (magit-git "config" "--add" "a.b" "val2")
+   ;; CamelCase variable names.
+   (magit-git "config" "Cam.El.Case.Var" "value")
+   ;; Values with newlines.
+   (magit-git "config" "a.b2" "line1\nline2")
+   ;; Config variables in submodules.
+   (magit-git "submodule" "add" "../remote" "repo/")
+
+   (magit-test-magit-get)
+   (let ((magit--refresh-cache (list (cons 0 0))))
+     (magit-test-magit-get))))
+
 (ert-deftest magit-get-boolean ()
   (magit-with-test-repository
     (magit-git "config" "a.b" "true")