gnu: ocaml-seq: Don't use unstable tarball.

* gnu/packages/ocaml.scm (ocaml-seq)[source]: Use GIT-FETCH and
GIT-FILE-NAME.
Fix indentation.

gnu/packages/ocaml.scm

@@ -3508,14 +3508,15 @@ new record values.")
   (package
     (name "ocaml-seq")
     (version "0.1")
-    (source (origin
-              (method url-fetch)
-              (uri (string-append "https://github.com/c-cube/seq/archive/"
-                                  version ".tar.gz"))
-              (file-name (string-append name "-" version ".tar.gz"))
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/c-cube/seq.git")
+             (commit version)))
+       (file-name (git-file-name name version))
        (sha256
-               (base32
-                "02lb2d9i12bxrz2ba5wygk2bycan316skqlyri0597q7j9210g8r"))))
+        (base32 "1cjpsc7q76yfgq9iyvswxgic4kfq2vcqdlmxjdjgd4lx87zvcwrv"))))
     (build-system ocaml-build-system)
     (arguments
      `(#:tests? #f