racket-repl: Re-implement as just running a file; closes #689

Narrowly, this fixes the kind of problem as in #689 where a setting
like racket-pretty-print only takes effect via a run.

Broadly, this makes this command follow the the main intended use case
-- a REPL is associated with running a file. Now the command is just a
shortcut for running a file with a certain name (and creating that
file if it doesn't exist).

Also, this fits better in a hash-lang world. If say someone mostly
works with #lang rhombus, and wants "give me a quick REPL" to use
that, now they can instead of getting #lang racket/base.

Finally, this lets the doc string explain that the REPL is always
just about running some file. If a user wanted to have "several init
files", well, they're really talking about running several source
files frequently, which of course they can already do. And if they
want a quick key binding for each one, that's an easy customization
nearly any end user can do for themselves.

TL;DR: Years ago when some folks asked for a racket-repl command, this
is probably how I should have done it: A trivial variation of
racket-run.

doc/generate.el

@@ -204,6 +204,7 @@
     racket-images-keep-last
     racket-images-system-viewer
     racket-pretty-print
+    racket-repl-command-file
     "Other variables"
     racket-indent-curly-as-sequence
     racket-indent-sequence-depth

doc/racket-mode.texi

@@ -226,6 +226,7 @@ REPL variables
 * racket-images-keep-last::
 * racket-images-system-viewer::
 * racket-pretty-print::
+* racket-repl-command-file::
 
 Other variables
 
@@ -2325,22 +2326,18 @@ simply the outermost, file module.
 
 Show a Racket REPL buffer in some window.
 
-@strong{IMPORTANT}
-
 The main, intended use of Racket Mode's REPL is that you
-@code{find-file} some specific .rkt file, then run it using
+@code{find-file} some specific file, then run it using a command like
 @ref{racket-run} or @ref{racket-run-module-at-point}. The resulting REPL
 will correspond to those definitions and match your expectations.
 
-If you really want to start a REPL for no file in particular,
-then you could use this @ref{racket-repl} command. But the resulting
-REPL will have a minimal ``#lang racket/base'' namespace. You
-could enter ``(require racket)'' if you want the equivalent of
-``#lang racket''. You could also ``(require racket/enter)'' if
-you want things like ``enter!''. But in some sense you'd be
-``using it wrong''. If you actually don't want to use Racket
-Mode's REPL as intended, then consider using a plain Emacs
-@code{shell} buffer to run command-line Racket.
+Therefore this @ref{racket-repl} command -- which is intended as a
+convenience for people who want a way to ``just get a quick
+REPL'' -- is actually implemented as just running the file named
+in the customization variable @ref{racket-repl-command-file}. By
+default when that file doesn't exist, it is created to contain
+just ``#lang racket/base''. You may edit the file to use a
+different lang, require other modules, or whatever.
 
 @node racket-repl-describe
 @subsection racket-repl-describe
@@ -3304,6 +3301,7 @@ classic @ref{racket-mode} for rackety module languages:
 * racket-images-keep-last::
 * racket-images-system-viewer::
 * racket-pretty-print::
+* racket-repl-command-file::
 @end menu
 
 @node racket-repl-buffer-name-function
@@ -3401,6 +3399,11 @@ The image viewer program to use for @code{racket-view-image}.
 
 Use pretty-print instead of print in REPL@?
 
+@node racket-repl-command-file
+@subsection racket-repl-command-file
+
+Name of the file used by @ref{racket-repl}.
+
 @node Other variables
 @section Other variables
 

racket-custom.el

@@ -392,7 +392,6 @@ will use this to decide whether to submit your input, yet."
   :safe #'booleanp
   :group 'racket-repl)
 
-
 (defcustom racket-before-run-hook nil
   "Normal hook done before various Racket Mode run commands.
 
@@ -423,6 +422,14 @@ from the variable `racket-repl-buffer-name'."
   :risky t
   :group 'racket-repl)
 
+(defcustom racket-repl-command-file
+  (expand-file-name "repl.rkt"
+                    (locate-user-emacs-file (file-name-as-directory "racket-mode")))
+  "Name of the file used by `racket-repl'."
+  :tag "REPL Command File"
+  :type 'file
+  :group 'racket-repl)
+
 ;;; Other
 
 (defgroup racket-other nil

racket-repl.el

@@ -508,30 +508,38 @@ even when the module language doesn't provide any binding for
 (defun racket-repl (&optional noselect)
   "Show a Racket REPL buffer in some window.
 
-*IMPORTANT*
-
 The main, intended use of Racket Mode's REPL is that you
-`find-file' some specific .rkt file, then run it using
+`find-file' some specific file, then run it using a command like
 `racket-run' or `racket-run-module-at-point'. The resulting REPL
 will correspond to those definitions and match your expectations.
 
-If you really want to start a REPL for no file in particular,
-then you could use this `racket-repl' command. But the resulting
-REPL will have a minimal \"#lang racket/base\" namespace. You
-could enter \"(require racket)\" if you want the equivalent of
-\"#lang racket\". You could also \"(require racket/enter)\" if
-you want things like \"enter!\". But in some sense you'd be
-\"using it wrong\". If you actually don't want to use Racket
-Mode's REPL as intended, then consider using a plain Emacs
-`shell' buffer to run command-line Racket."
+Therefore this `racket-repl' command -- which is intended as a
+convenience for people who want a way to \"just get a quick
+REPL\" -- is actually implemented as just running the file named
+in the customization variable `racket-repl-command-file'. By
+default when that file doesn't exist, it is created to contain
+just \"#lang racket/base\". You may edit the file to use a
+different lang, require other modules, or whatever."
   (interactive "P")
-  (racket-call-racket-repl-buffer-name-function)
-  (racket--repl-ensure-buffer-and-session
-   nil
-   (lambda (repl-buffer)
-     (racket--repl-refresh-namespace-symbols)
-     (unless noselect
-       (select-window (get-buffer-window repl-buffer t))))))
+  ;; Create file if it doesn't exist
+  (unless (file-exists-p racket-repl-command-file)
+    (let ((dir (file-name-directory racket-repl-command-file)))
+      (unless (file-exists-p dir)
+        (make-directory dir t)))
+    (write-region ";; Used by M-x racket-repl; you may edit\n#lang racket/base\n"
+                  nil racket-repl-command-file))
+  ;; Visit the file without selecting it, and run it.
+  (with-current-buffer (find-file-noselect racket-repl-command-file)
+    (let ((name (format "*Racket REPL <%s>*" racket-repl-command-file)))
+      (setq-local racket-repl-buffer-name name))
+    (racket--repl-run
+     (list racket-repl-command-file)
+     nil
+     nil
+     (lambda ()
+       (display-buffer racket-repl-buffer-name)
+       (unless noselect
+         (select-window (get-buffer-window racket-repl-buffer-name t)))))))
 
 ;;; Run