home: services: Add home-special-file-service-type (which allows declaring symlinks to any kind of file, not only those in the store)

radix/home/services.scm

@@ -1,12 +1,26 @@
 (define-module (radix home services)
-  #:export (use-home-service-modules))
+  #:use-module (guix gexp)
+  #:use-module (gnu home services)
+  #:use-module (gnu services)
+  #:use-module (srfi srfi-1)
+  #:export (home-special-files-service-type))
 
-(define service-module-hint
-  (@@ (gnu) service-module-hint))
-
-(define-syntax-rule (try-use-modules hint modules ...)
-  ((@@ (gnu) try-use-modules) hint modules ...))
-
-(define-syntax-rule (use-home-service-modules module ...)
-  (try-use-modules service-module-hint
-                   (gnu home services module) ...))
+(define home-special-files-service-type
+  (service-type
+   (name 'home-special-files)
+   (extensions
+    (list (service-extension
+           home-activation-service-type
+           (lambda (files)
+             #~(for-each
+                 ((@ (ice-9 match) match-lambda)
+                   ((target file)
+                    (let* ((target (string-append (getenv "HOME") "/" target))
+                           (pivot (string-append target ".new")))
+                      (mkdir-p (dirname target))
+                      (symlink file pivot)
+                      (rename-file pivot target))))
+                 '#$files)))))
+   (compose concatenate)
+   (extend append)
+   (description "Add special files to your home directory.")))