store: The 'references' parameter of 'add-text-to-store' is now optional.

* guix/store.scm (add-text-to-store): Make 'references' optional.
* tests/store.scm ("dead-paths", "references"): Use 'add-text-to-store'
  with no optional argument.
* doc/guix.texi (The Store): Adjust accordingly.

doc/guix.texi

@@ -1061,7 +1061,7 @@ argument.
 Return @code{#t} when @var{path} is a valid store path.
 @end deffn
 
-@deffn {Scheme Procedure} add-text-to-store @var{server} @var{name} @var{text} @var{references}
+@deffn {Scheme Procedure} add-text-to-store @var{server} @var{name} @var{text} [@var{references}]
 Add @var{text} under file @var{name} in the store, and return its store
 path.  @var{references} is the list of store paths referred to by the
 resulting store path.

guix/store.scm

@@ -452,7 +452,7 @@ encoding conversion errors."
                                        (string-list references))
                     #f
                     store-path)))
-    (lambda (server name text references)
+    (lambda* (server name text #:optional (references '()))
       "Add TEXT under file NAME in the store, and return its store path.
 REFERENCES is the list of store paths referred to by the resulting store
 path."

tests/store.scm

@@ -68,8 +68,7 @@
 (test-skip (if %store 0 10))
 
 (test-assert "dead-paths"
-  (let ((p (add-text-to-store %store "random-text"
-                              (random-text) '())))
+  (let ((p (add-text-to-store %store "random-text" (random-text))))
     (member p (dead-paths %store))))
 
 ;; FIXME: Find a test for `live-paths'.
@@ -99,7 +98,7 @@
 
 (test-assert "references"
   (let* ((t1 (add-text-to-store %store "random1"
-                                (random-text) '()))
+                                (random-text)))
          (t2 (add-text-to-store %store "random2"
                                 (random-text) (list t1))))
     (and (equal? (list t1) (references %store t2))