substitute-binary: Implement `--substitute'.

This allows build outputs to be transparently downloaded from
http://hydra.gnu.org, for example.

* config-daemon.ac: Check for `gzip', `bzip2', and `xz'.
* guix/config.scm.in (%gzip, %bzip2, %xz): New variable.
* guix/scripts/substitute-binary.scm (fetch): Return SIZE as a second value.
  (<narinfo>): Change `url' to `uri'.
  (make-narinfo): Rename to...
  (narinfo-maker): ... this.  Handle relative URLs.
  (fetch-narinfo): Adjust accordingly.
  (filtered-port, decompressed-port): New procedures.
  (guix-substitute-binary): Implement the `--substitute' case.
* tests/store.scm ("substitute query"): Use (%store-prefix) instead
  of (getenv "NIX_STORE_DIR").
  ("substitute"): New test.

1 files changed, 13 insertions, 1 deletions

diff --git a/guix/config.scm.in b/guix/config.scm.in
index ab7b0669b8..772ea8c289 100644
--- a/guix/config.scm.in
+++ b/guix/config.scm.in
@@ -26,7 +26,10 @@
             %system
             %libgcrypt
             %nixpkgs
-            %nix-instantiate))
+            %nix-instantiate
+            %gzip
+            %bzip2
+            %xz))
 
 ;;; Commentary:
 ;;;
@@ -67,4 +70,13 @@
 (define %nix-instantiate
   "@NIX_INSTANTIATE@")
 
+(define %gzip
+  "@GZIP@")
+
+(define %bzip2
+  "@BZIP2@")
+
+(define %xz
+  "@XZ@")
+
 ;;; config.scm ends here