nix-prefetch-github: init

krebs/5pkgs/simple/nix-prefetch-github.nix

@@ -0,0 +1,25 @@
+{ curl, jq, nix, writeDashBin }:
+
+writeDashBin "nix-prefetch-github" ''
+  # usage: nix-prefetch-github OWNER REPO [REF]
+  set -efu
+
+  owner=$1
+  repo=$2
+  ref=''${3-master}
+
+  info_url=https://api.github.com/repos/$owner/$repo/commits/$ref
+  info=$(${curl}/bin/curl -fsS "$info_url")
+  rev=$(printf %s "$info" | ${jq}/bin/jq -r .sha)
+
+  name=$owner-$repo-$ref
+  url=https://github.com/$owner/$repo/tarball/$rev
+  sha256=$(${nix}/bin/nix-prefetch-url --name "$name" --unpack "$url")
+
+  export owner repo rev sha256
+  ${jq}/bin/jq -n '
+    env | {
+      owner, repo, rev, sha256
+    }
+  '
+''