publish: Add support for zstd compression.

* guix/scripts/publish.scm (compress-nar)[write-compressed-file]: New
procedure.
Use it for 'gzip' and 'lzip'.  Add 'zstd.
(nar-response-port, string->compression-type): Add case for 'zstd'.
* tests/publish.scm (zstd-supported?): New procedure.
("/nar/zstd/*"): New test.
* doc/guix.texi (Invoking guix publish): Document zstd compression.
(Base Services): Add cross-reference to the above node.

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/publish.scm b/tests/publish.scm
index cafd0f13a2..52101876b5 100644
--- a/tests/publish.scm
+++ b/tests/publish.scm
@@ -38,6 +38,7 @@
   #:use-module ((guix pki) #:select (%public-key-file %private-key-file))
   #:use-module (zlib)
   #:use-module (lzlib)
+  #:autoload   (zstd) (call-with-zstd-input-port)
   #:use-module (web uri)
   #:use-module (web client)
   #:use-module (web response)
@@ -54,6 +55,9 @@
 (define %store
   (open-connection-for-tests))
 
+(define (zstd-supported?)
+  (resolve-module '(zstd) #t #f #:ensure #f))
+
 (define %reference (add-text-to-store %store "ref" "foo"))
 
 (define %item (add-text-to-store %store "item" "bar" (list %reference)))
@@ -237,6 +241,18 @@ References: ~%"
          (cut restore-file <> temp)))
      (call-with-input-file temp read-string))))
 
+(unless (zstd-supported?) (test-skip 1))
+(test-equal "/nar/zstd/*"
+  "bar"
+  (call-with-temporary-output-file
+   (lambda (temp port)
+     (let ((nar (http-get-port
+                 (publish-uri
+                  (string-append "/nar/zstd/" (basename %item))))))
+       (call-with-zstd-input-port nar
+         (cut restore-file <> temp)))
+     (call-with-input-file temp read-string))))
+
 (test-equal "/*.narinfo with compression"
   `(("StorePath" . ,%item)
     ("URL" . ,(string-append "nar/gzip/" (basename %item)))