utils: Move 'package-name->name+version' to (guix build utils).

* guix/utils.scm (package-name->name+version): Move to...
* guix/build/utils.scm (package-name->name+version): ... here.  New
  procedure.
* guix/build/emacs-build-system.scm (package-name->name+version):
  Remove.

guix/build/emacs-build-system.scm

@@ -150,28 +150,6 @@ second hyphen.  This corresponds to 'name-version' as used in ELPA packages."
             strip-store-file-name)
    store-dir))
 
-;; from (guix utils).  Should we put it in (guix build utils)?
-(define (package-name->name+version name)
-  "Given NAME, a package name like \"foo-0.9.1b\", return two values:
-\"foo\" and \"0.9.1b\".  When the version part is unavailable, NAME and
-#f are returned.  The first hyphen followed by a digit is considered to
-introduce the version part."
-  ;; See also `DrvName' in Nix.
-
-  (define number?
-    (cut char-set-contains? char-set:digit <>))
-
-  (let loop ((chars   (string->list name))
-             (prefix '()))
-    (match chars
-      (()
-       (values name #f))
-      ((#\- (? number? n) rest ...)
-       (values (list->string (reverse prefix))
-               (list->string (cons n rest))))
-      ((head tail ...)
-       (loop tail (cons head prefix))))))
-
 (define %standard-phases
   (modify-phases gnu:%standard-phases
     (delete 'configure)

guix/build/utils.scm

@@ -21,6 +21,7 @@
 (define-module (guix build utils)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-60)
   #:use-module (ice-9 ftw)
   #:use-module (ice-9 match)
@@ -34,6 +35,7 @@
   #:export (%store-directory
             store-file-name?
             strip-store-file-name
+            package-name->name+version
             parallel-job-count
 
             directory-exists?
@@ -94,6 +96,27 @@ is typically a \"PACKAGE-VERSION\" string."
   (string-drop file
                (+ 34 (string-length (%store-directory)))))
 
+(define (package-name->name+version name)
+  "Given NAME, a package name like \"foo-0.9.1b\", return two values:
+\"foo\" and \"0.9.1b\".  When the version part is unavailable, NAME and
+#f are returned.  The first hyphen followed by a digit is considered to
+introduce the version part."
+  ;; See also `DrvName' in Nix.
+
+  (define number?
+    (cut char-set-contains? char-set:digit <>))
+
+  (let loop ((chars   (string->list name))
+             (prefix '()))
+    (match chars
+      (()
+       (values name #f))
+      ((#\- (? number? n) rest ...)
+       (values (list->string (reverse prefix))
+               (list->string (cons n rest))))
+      ((head tail ...)
+       (loop tail (cons head prefix))))))
+
 (define parallel-job-count
   ;; Number of processes to be passed next to GNU Make's `-j' argument.
   (make-parameter

guix/utils.scm

@@ -29,7 +29,8 @@
   #:use-module (srfi srfi-60)
   #:use-module (rnrs bytevectors)
   #:use-module ((rnrs io ports) #:select (put-bytevector))
-  #:use-module ((guix build utils) #:select (dump-port))
+  #:use-module ((guix build utils)
+                #:select (dump-port package-name->name+version))
   #:use-module ((guix build syscalls) #:select (errno mkdtemp!))
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 format)
@@ -39,6 +40,7 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 format)
   #:use-module (system foreign)
+  #:re-export (package-name->name+version)
   #:export (bytevector->base16-string
             base16-string->bytevector
 
@@ -71,7 +73,6 @@
             version-prefix
             version-major+minor
             guile-version>?
-            package-name->name+version
             string-replace-substring
             arguments-from-environment-variable
             file-extension
@@ -573,27 +574,6 @@ minor version numbers from version-string."
                             (micro-version))
              str))
 
-(define (package-name->name+version name)
-  "Given NAME, a package name like \"foo-0.9.1b\", return two values:
-\"foo\" and \"0.9.1b\".  When the version part is unavailable, NAME and
-#f are returned.  The first hyphen followed by a digit is considered to
-introduce the version part."
-  ;; See also `DrvName' in Nix.
-
-  (define number?
-    (cut char-set-contains? char-set:digit <>))
-
-  (let loop ((chars   (string->list name))
-             (prefix '()))
-    (match chars
-      (()
-       (values name #f))
-      ((#\- (? number? n) rest ...)
-       (values (list->string (reverse prefix))
-               (list->string (cons n rest))))
-      ((head tail ...)
-       (loop tail (cons head prefix))))))
-
 (define (file-extension file)
   "Return the extension of FILE or #f if there is none."
   (let ((dot (string-rindex file #\.)))