utils: Add `guile-version>?', and use it.

This fixes Guile version comparisons when (version) has a
vendor-specific suffix.

Reported by Andreas Enge <andreas@enge.fr>.

* guix/utils.scm (guile-version>?): New procedure.
* tests/utils.scm ("guile-version>? 1.8", "guile-version>? 10.5"): New
  tests.
* guix/scripts/substitute-binary.scm (fetch, progress-report-port): Use
  `guile-version>?' instead of `version>?'.
* guix/http-client.scm (when-guile<=2.0.5, http-fetch): Likewise.

guix/http-client.scm

@@ -133,7 +133,7 @@ (define bad-response
              (get-bytevector-all (response-port r))))))
 
  ;; Install this patch only on Guile 2.0.5.
- (when (version>? "2.0.6" (version))
+ (unless (guile-version>? "2.0.5")
    (module-set! (resolve-module '(web response))
                 'read-response-body read-response-body*)))
 
@@ -163,7 +163,7 @@ (define* (http-fetch uri #:key port (text? #f) (buffered? #t))
                      ;; Try hard to use the API du jour to get an input port.
                      ;; On Guile 2.0.5 and before, we can only get a string or
                      ;; bytevector, and not an input port.  Work around that.
-                     (if (version>? (version) "2.0.7")
+                     (if (guile-version>? "2.0.7")
                          (http-get uri #:streaming? #t #:port port) ; 2.0.9+
                          (if (defined? 'http-get*)
                              (http-get* uri #:decode-body? text?

guix/scripts/substitute-binary.scm

@@ -155,7 +155,7 @@ (define* (fetch uri #:key (buffered? #t) (timeout? #t))
      ;; and then cancel with:
      ;;   sudo tc qdisc del dev eth0 root
      (let ((port #f))
-       (with-timeout (if (or timeout? (version>? (version) "2.0.5"))
+       (with-timeout (if (or timeout? (guile-version>? "2.0.5"))
                          %fetch-timeout
                          0)
          (begin
@@ -417,7 +417,7 @@ (define (read! bv start count)
 
   ;; Since `http-fetch' in Guile 2.0.5 returns all the data once it's done,
   ;; don't pretend to report any progress in that case.
-  (if (version>? (version) "2.0.5")
+  (if (guile-version>? "2.0.5")
       (make-custom-binary-input-port "progress-port-proc"
                                      read! #f #f
                                      (cut close-port port))

guix/utils.scm

@@ -59,6 +59,7 @@ (define-module (guix utils)
             %current-target-system
             version-compare
             version>?
+            guile-version>?
             package-name->name+version
             string-tokenize*
             file-extension
@@ -316,6 +317,15 @@ (define (version>? a b)
   "Return #t when A denotes a newer version than B."
   (eq? '> (version-compare a b)))
 
+(define (guile-version>? str)
+  "Return #t if the running Guile version is greater than STR."
+  ;; Note: Using (version>? (version) "2.0.5") or similar doesn't work,
+  ;; because the result of (version) can have a prefix, like "2.0.5-deb1".
+  (version>? (string-append (major-version) "."
+                            (minor-version) "."
+                            (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

tests/utils.scm

@@ -66,6 +66,12 @@ (define-module (test-utils)
            ("nixpkgs" "1.0pre22125_a28fe19")
            ("gtk2" "2.38.0"))))
 
+(test-assert "guile-version>? 1.8"
+  (guile-version>? "1.8"))
+
+(test-assert "guile-version>? 10.5"
+  (not (guile-version>? "10.5")))
+
 (test-equal "string-tokenize*"
   '(("foo")
     ("foo" "bar" "baz")