scripts: repl: Add -i, --interactive flag.

* guix/scripts/repl.scm (%options): Add -i, --interactive flag.
(guix-repl): Honor -i, --interactive flag.
* doc/guix.texi (Invoking guix repl): Add documentation for -i, --interactive.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>

doc/guix.texi

@@ -111,6 +111,7 @@ Copyright @copyright{} 2022 (@*
 Copyright @copyright{} 2022 John Kehayias@*
 Copyright @copyright{} 2022 Ivan Vilata-i-Balaguer@*
 Copyright @copyright{} 2023 Giacomo Leidi@*
+Copyright @copyright{} 2022 Antero Mejr <antero@mailbox.org>
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -12012,6 +12013,14 @@ lines at the top of the script:
 @code{!#}
 @end example
 
+To make a script that launches an interactive REPL directly from the
+shell, use the @code{--interactive} flag:
+
+@example
+@code{#!/usr/bin/env -S guix repl --interactive}
+@code{!#}
+@end example
+
 Without a file name argument, a Guile REPL is started, allowing for
 interactive use (@pxref{Using Guix Interactively}):
 
@@ -12060,6 +12069,10 @@ Accept connections on localhost on port 37146.
 Accept connections on the Unix-domain socket @file{/tmp/socket}.
 @end table
 
+@item --interactive
+@itemx -i
+Launch the interactive REPL after @var{file} is executed.
+
 @item --load-path=@var{directory}
 @itemx -L @var{directory}
 Add @var{directory} to the front of the package module search path

guix/scripts/repl.scm

@@ -62,6 +62,9 @@ (define %options
         (option '(#\q) #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'ignore-dot-guile? #t result)))
+        (option '(#\i "interactive") #f #f
+                (lambda (opt name arg result)
+                  (alist-cons 'interactive? #t result)))
         (option '(#\L "load-path") #t #f
                 (lambda (opt name arg result)
                   ;; XXX: Imperatively modify the search paths.
@@ -84,6 +87,9 @@ (define (show-help)
   -q                     inhibit loading of ~/.guile"))
   (newline)
   (display (G_ "
+  -i, --interactive      launch REPL after evaluating FILE"))
+  (newline)
+  (display (G_ "
   -L, --load-path=DIR    prepend DIR to the package module search path"))
   (newline)
   (display (G_ "
@@ -196,7 +202,7 @@ (define script
          ;; file in %LOAD-PATH.  Thus, pass (getcwd) instead of ".".
          (load-in-vicinity (getcwd) (car script)))))
 
-    (when (null? script)
+    (when (or (null? script) (assoc-ref opts 'interactive?))
       ;; Start REPL
       (let ((type (assoc-ref opts 'type)))
         (call-with-connection (assoc-ref opts 'listen)