Hello Guix,

I rewrote the recursive-import-semver procedure to use the new
topological-sort procedure. I also return a list instead of a stream
like (recursive-import). So to recap (recursive-import-semver) imports
dependency using semantic version to find the correct version of a
dependency. The crate importer has also be converted to use
recursive-import-semver. It will now use recursive-import-semver when
"guix import crate -r" is used. You can also specify the range that you
would like to import such as guix import crate -r rand@^0.6". Here is an
example of the format that it will produce. 

(define-public rust-bincode-1.2.1
  (package
    (name "rust-bincode")
    (version "1.2.1")
    (source
      (origin
        (method url-fetch)
        (uri (crate-uri "bincode" version))
        (file-name
          (string-append name "-" version ".crate"))
        (sha256
          (base32
            "1gvxm3n67xv1874fwxmnlircdlphlk1hcw75ykrrnw9l2nky4lsp"))))
    (build-system cargo-build-system)
    (arguments
      `(#:skip-build?
        #t
        #:cargo-inputs
        (("rust-byteorder-1.3.2" ,rust-byteorder-1.3.2)
         ("rust-serde-1.0.103" ,rust-serde-1.0.103))))
    (home-page "https://github.com/servo/bincode")
    (synopsis
      "A binary serialization / deserialization strategy that uses Serde
for transforming structs into bytes and vice versa!")
    (description
      "This package provides a binary serialization / deserialization
strategy that uses Serde for transforming structs into bytes and vice
versa!")
    (license license:expat)))

-Martin