gnu: python-ghp-import: Don't use unstable tarball.

* gnu/packages/version-control.scm (python-ghp-import)[source]: Use GIT-FETCH and
GIT-FILE-NAME.

gnu/packages/version-control.scm

@@ -772,14 +772,13 @@ a built-in cache to decrease server I/O pressure.")
     (version "0.5.5")
     (source
      (origin
-       (method url-fetch)
-       (uri (string-append
-             "https://github.com/davisp/ghp-import/archive/"
-             version ".tar.gz"))
-       (file-name (string-append name "-" version ".tar.gz"))
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/davisp/ghp-import.git")
+             (commit version)))
+       (file-name (git-file-name name version))
        (sha256
-        (base32
-         "0x887v690xsac2hzjkpbvp3a6crh3m08mqbk3nb4xwc9dnk869q7"))))
+        (base32 "12pmw3zz3i57ljnm0rxdyjqdyhisbvy18mjwkb3bzp5pgzs2f45c"))))
     (build-system python-build-system)
     (arguments
      `(#:phases (modify-phases %standard-phases