perf(magit): minor optimizations

- Resolves `magit-git-executable` ahead of time. We used to do this, but
  back then, magit used `magit-git-executable` in TRAMP sessions too.
  Now, magit has a separate `magit-remote-git-executable` variable.
- Only invalidate projectile cache if the magit status buffer's contents
  has changed. This will prevent excessive (and potentially expensive)
  `projectile-invalidate-cache` calls for trivial changes, l
- Avoid changing the active buffer when fetching a specific variable
  from a buffer is enough (more cpu/mem efficient).
- Don't adjust the fringe if the fringes are already the requested size.

modules/tools/magit/config.el

@@ -66,23 +66,32 @@ FUNCTION
         ;; each, and the two projects happen to have the same name! By unsetting
         ;; `magit-uniquify-buffer-names', magit uses the project's full path as
         ;; its name, preventing such naming collisions.
-        magit-uniquify-buffer-names nil)
+        magit-uniquify-buffer-names nil
+        ;; PERF: Magit calls (and resolves) `magit-git-executable' frequently
+        ;;   enough that a non-absolute path can notably slow it down,
+        ;;   especially on MacOS and Windows, so I resolve it once, the first
+        ;;   time it's needed.
+        magit-git-executable (or (executable-find magit-git-executable) "git"))
 
   ;; Turn ref links into clickable buttons.
   (add-hook 'magit-process-mode-hook #'goto-address-mode)
 
   ;; Since the project likely now contains new files, purge the projectile cache
   ;; so `projectile-find-file' et all don't produce an stale file list.
+  (defvar +magit--last-hash nil)
   (add-hook! 'magit-refresh-buffer-hook
     (defun +magit-invalidate-projectile-cache-h ()
       ;; Only invalidate the hot cache and nothing else (everything else is
       ;; expensive busy work, and we don't want to slow down magit's
       ;; refreshing).
-      (let (projectile-require-project-root
+      (let ((hash (buffer-hash))
+            projectile-require-project-root
             projectile-enable-caching
             projectile-verbose)
-        (letf! ((#'recentf-cleanup #'ignore))
-          (projectile-invalidate-cache nil)))))
+        (unless (equal +magit--last-hash hash)
+          (letf! ((#'recentf-cleanup #'ignore))
+            (projectile-invalidate-cache nil))
+          (setq-local +magit--last-hash hash)))))
   ;; Use a more efficient strategy to auto-revert buffers whose git state has
   ;; changed: refresh the visible buffers immediately...
   (add-hook 'magit-post-refresh-hook #'+magit-mark-stale-buffers-h)
@@ -142,9 +151,9 @@ FUNCTION
   ;; so magit buffers can be switched to (except for process buffers)
   (add-hook! 'doom-real-buffer-functions
     (defun +magit-buffer-p (buf)
-      (with-current-buffer buf
-        (and (derived-mode-p 'magit-mode)
-             (not (eq major-mode 'magit-process-mode))))))
+      (let ((mode (buffer-local-value 'major-mode buf)))
+        (and (provided-mode-derived-p mode 'magit-mode)
+             (not (eq mode 'magit-process-mode))))))
 
   ;; Clean up after magit by killing leftover magit buffers and reverting
   ;; affected buffers (or at least marking them as need-to-be-reverted).
@@ -154,16 +163,19 @@ FUNCTION
   ;; Close transient with ESC
   (define-key transient-map [escape] #'transient-quit-one)
 
+  (defun +magit-enlargen-fringe-h ()
+    "Make fringe larger in magit."
+    (and (display-graphic-p)
+         (derived-mode-p 'magit-section-mode)
+         +magit-fringe-size
+         (let ((left  (or (car-safe +magit-fringe-size) +magit-fringe-size))
+               (right (or (cdr-safe +magit-fringe-size) +magit-fringe-size)))
+           (unless (and (= left  (or left-fringe-width 0))
+                        (= right (or right-fringe-width 0)))
+             (set-window-fringes nil left right)))))
   (add-hook! 'magit-section-mode-hook
     (add-hook! 'window-configuration-change-hook :local
-      (defun +magit-enlargen-fringe-h ()
-        "Make fringe larger in magit."
-        (and (display-graphic-p)
-             (derived-mode-p 'magit-section-mode)
-             +magit-fringe-size
-             (let ((left  (or (car-safe +magit-fringe-size) +magit-fringe-size))
-                   (right (or (cdr-safe +magit-fringe-size) +magit-fringe-size)))
-               (set-window-fringes nil left right))))))
+      #'+magit-enlargen-fringe-h))
 
   (add-hook! 'magit-diff-visit-file-hook
     (defun +magit-reveal-point-if-invisible-h ()