Tweak text and code of the "Go Programming" section

README.org

@@ -668,7 +668,7 @@ for technical information.
                  display-buffer-pop-up-window
                  (inhibit-same-window . t)))
   (add-to-list 'display-buffer-alist
-               `(,(rx (or "*Gofmt*" "*Occur*" "*grep*" "*xref*"))
+               `(,(rx (or "*Occur*" "*grep*" "*xref*"))
                  display-buffer-reuse-window
                  (inhibit-same-window . nil)))
   ;; BUG#70773: Eli tells `(setq delayed-warnings-hook nil)' is better.
@@ -4503,14 +4503,20 @@ Links to learn [[https://go.dev/][Go]] are:
 1. [[https://www.golangprograms.com/go-language.html][Go programming language]] contains a tutorial and a reference.
 2. [[https://gobyexample.com/][Go by example]] is a showcase of short examples with explanations.
 3. [[https://interpreterbook.com/][Writing An Interpreter In Go]] is book showing how to write a real program.
+Listing [[lst:setup-go]] defines:
+- =gotsfmt= which is a cheap small replacement for =gofmt= in [[https://github.com/dominikh/go-mode.el][go-mode]]. Adding
+  =gofmt= to =before-save-hook= is safe, but adding =gotsfmt= to it is unsafe
+  because =gotsfmt= calls =save-buffer=.
+- =gots8tabs= which sets tab stops to the default 8 spaces locally in the
+  current buffer if the major mode is =go-ts-mode=.
+- =gots2tabs= which sets tab stops to 2 spaces locally in the current buffer if
+  the major mode is =go-ts-mode=.
 
 #+caption[Setup Go programming]:
 #+caption: Setup Go programming.
 #+name: lst:setup-go
 #+begin_src emacs-lisp -n :results silent
 (when (featurep 'treesit)
-  (setopt go-ts-mode-indent-offset 8) ; for compatibility with Go tools.
-
   (defun gots2tabs ()
     "Set tab stops to 2 spaces in current `go-ts` buffer."
     (interactive)
@@ -4523,32 +4529,37 @@ Links to learn [[https://go.dev/][Go]] are:
     (interactive)
     (when (eq major-mode 'go-ts-mode)
       (setq-local go-ts-mode-indent-offset 8)
-      (setq-local tab-width 9)))
+      (setq-local tab-width 8)))
 
   (defun gotsfmt ()
     "Let `gofmt` format current `go-ts` buffer and file."
     (interactive)
     (when (eq major-mode 'go-ts-mode)
-      (save-buffer)
-      (let ((cb (current-buffer))
-            (pb (get-buffer-create "*Gofmt*"))
-            (fn (buffer-file-name)))
-        (set-buffer pb)
+      (let ((source (current-buffer))
+            (goal (get-buffer-create "*Gofmt Output*"))
+            (filename (buffer-file-name)))
+        (when (eq t (buffer-modified-p source)) ; autosaved is not OK.
+          (save-buffer))
+        (set-buffer goal)
         (erase-buffer)
-        (if (zerop (call-process "gofmt" nil t nil "-d" fn))
+        ;; Direct stdin and stderr to goal.
+        ;; Get goal with filename in patch by calling "gofmt -d filename".
+        ;; Provoke a gofmt error (delete package statement) to debug this.
+        (if (zerop (call-process "gofmt" nil t nil "-d" filename))
             (if (> (point) (point-min))
                 (progn
-                  (display-buffer pb)
-                  (switch-to-buffer pb)
-                  (diff-apply-hunk)
-                  (set-buffer cb)
+                  (diff-apply-buffer)
+                  (set-buffer source)
                   (save-buffer)
                   (message "Gofmt tabbed your code!"))
               (message "Gofmt adores your code!"))
-          (display-buffer pb)
-          (switch-to-buffer pb)
+          (display-buffer goal)
           (message "Your code chokes Gofmt!")))))
 
+  (add-to-list 'display-buffer-alist `("*Gofmt Output*"
+                                       display-buffer-reuse-window
+                                       (inhibit-same-window . nil)))
+
   (add-to-list 'auto-mode-alist `(,(rx ".go" eos) . go-ts-mode)))
 #+end_src