emacs: Add completions for '--type' option of 'refresh' popup.

* guix/scripts/refresh.scm: Export '%updaters'.
* emacs/guix-main.scm (refresh-updater-names): New procedure.
* emacs/guix-base.el (guix-refresh-updater-names): New function.
* emacs/guix-read.el (guix-read-refresh-updater-names,
  guix-read-refresh-updater-names-string): New functions.
* emacs/guix-command.el (guix-command-improve-refresh-argument): Use
  'guix-read-refresh-updater-names-string'.

emacs/guix-base.el

@@ -186,6 +186,10 @@ For the meaning of location, see `guix-find-location'."
   "Return a list of names of available graph node types."
   (guix-eval-read (guix-make-guile-expression 'graph-type-names)))
 
+(guix-memoized-defun guix-refresh-updater-names ()
+  "Return a list of names of available refresh updater types."
+  (guix-eval-read (guix-make-guile-expression 'refresh-updater-names)))
+
 (guix-memoized-defun guix-lint-checker-names ()
   "Return a list of names of available lint checkers."
   (guix-eval-read (guix-make-guile-expression 'lint-checker-names)))

emacs/guix-command.el

@@ -241,6 +241,7 @@ to be modified."
 (guix-command-define-argument-improver
     guix-command-improve-refresh-argument
   '(("--select"     :fun guix-read-refresh-subset)
+    ("--type"       :fun guix-read-refresh-updater-names-string)
     ("--key-server" :char ?S)))
 
 (guix-command-define-argument-improver

emacs/guix-main.scm

@@ -991,6 +991,11 @@ Return #t if the shell command was executed successfully."
   "Return a list of names of available graph node types."
   (map node-type-name %node-types))
 
+(define (refresh-updater-names)
+  "Return a list of names of available refresh updater types."
+  (map (@ (guix upstream) upstream-updater-name)
+       (@ (guix scripts refresh) %updaters)))
+
 (define (lint-checker-names)
   "Return a list of names of available lint checkers."
   (map (lambda (checker)

emacs/guix-read.el

@@ -136,6 +136,12 @@ keywords are available:
  :single-reader guix-read-refresh-subset
  :single-prompt "Refresh subset: ")
 
+(guix-define-readers
+ :completions-getter guix-refresh-updater-names
+ :multiple-reader guix-read-refresh-updater-names
+ :multiple-prompt "Refresh updater,s: "
+ :multiple-separator ",")
+
 (guix-define-readers
  :completions-var guix-help-key-policies
  :single-reader guix-read-key-policy

guix/scripts/refresh.scm

@@ -42,7 +42,8 @@
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-37)
   #:use-module (rnrs io ports)
-  #:export (guix-refresh))
+  #:export (guix-refresh
+            %updaters))
 
 
 ;;;