gnu: subversion: Add package and rename former to subversion/pinned.

Subversion currently has CVEs. IMHO, it's unsafe to carry them around
in a profile. However, updating subversion potential leads to a lot of
rebuilds and I don't want to tackle this right now.

As for other packages, the way forward is to add a variant of the
package only used for svn-fetch, here subversion/pinned.

* gnu/packages/version-control.scm (subversion): Update to 1.14.5.
(subversion/pinned): Inherit from subversion, but build the exact same
derivation as the previous subversion variable.

* guix/svn-download.scm (subversion-package): Use subversion/pinned.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/version-control.scm

@@ -2992,14 +2992,14 @@ following features:
 (define-public subversion
   (package
     (name "subversion")
-    (version "1.14.3")
+    (version "1.14.5")
     (source (origin
               (method url-fetch)
               (uri (string-append "mirror://apache/subversion/"
                                   "subversion-" version ".tar.bz2"))
               (sha256
                (base32
-                "0h54l4p2dlk1rm4zm428hi6ij6xpqxqlqmvkhmz5yhq9392zv7ll"))))
+                "18a4avism0a7b1siikkm6v2snhanlmqqzl4p8hspp2vbfvkjk2p7"))))
     (build-system gnu-build-system)
     (arguments
      (list
@@ -3068,6 +3068,20 @@ usage; and its ability to support the needs of a wide variety of users and
 projects, from individuals to large-scale enterprise operations.")
     (license license:asl2.0)))
 
+(define-public subversion/pinned
+  (hidden-package
+   (package
+     (inherit subversion)
+     (name "subversion")
+     (version "1.14.3")
+     (source
+      (origin
+        (method url-fetch)
+        (uri (string-append "mirror://apache/subversion/"
+                            "subversion-" version ".tar.bz2"))
+        (sha256
+         (base32 "0h54l4p2dlk1rm4zm428hi6ij6xpqxqlqmvkhmz5yhq9392zv7ll")))))))
+
 (define-public rcs
   (package
     (name "rcs")

guix/svn-download.scm

@@ -72,7 +72,7 @@
 (define (subversion-package)
   "Return the default Subversion package."
   (let ((distro (resolve-interface '(gnu packages version-control))))
-    (module-ref distro 'subversion)))
+    (module-ref distro 'subversion/pinned)))
 
 (define (svn-fetch-builder svn hash-algo)
   (define guile-json