Running nixpkgs-update (https://nix-community.org/update-bot/) with UPDATE_INFO: docker-gc unstable-2015-10-5 -> 0.0.20170125 https://repology.org/project/docker-gc/versions
attrpath: docker-gc
Checking auto update branch...
No auto update branch exists
[version] 
[version] updated version and sha256
[rustCrateVersion] 
[rustCrateVersion] No cargoHash found
[golangModuleVersion] 
[golangModuleVersion] Not a buildGoModule package with vendorHash
[npmDepsVersion] 
[npmDepsVersion] No npmDepsHash
[updateScript] 
[updateScript] skipping because derivation has no updateScript
Diff after rewrites:
diff --git a/pkgs/applications/virtualization/docker/gc.nix b/pkgs/applications/virtualization/docker/gc.nix
index f6c7e9030a14..be71f5828d92 100644
--- a/pkgs/applications/virtualization/docker/gc.nix
+++ b/pkgs/applications/virtualization/docker/gc.nix
@@ -12,13 +12,13 @@
 }:
 stdenv.mkDerivation {
   pname = "docker-gc";
-  version = "unstable-2015-10-5";
+  version = "0.0.20170125";
 
   src = fetchFromGitHub {
     owner = "spotify";
     repo = "docker-gc";
     rev = "b0cc52aa3da2e2ac0080794e0be6e674b1f063fc";
-    sha256 = "07wf9yn0f771xkm3x12946x5rp83hxjkd70xgfgy35zvj27wskzm";
+    sha256 = "sha256-9U/Nj5D7l+Gfex2cNmWHA91cuiFJhD7q7OEcB6xPjh8=";
   };
 
   nativeBuildInputs = [ makeWrapper ];

Source url did not change.