Add tests for "git describe --long".

* Move test logic to scm-update.sh scripts.
    * Check for "git describe --long".

tests/jobs/deepgit-input.nix

@@ -0,0 +1,10 @@
+with import ./config.nix;
+{ src }:
+{  
+  copy = 
+    mkDerivation {
+      name = "git-input";
+      builder = ./scm-builder.sh;
+      inherit src;
+    };
+}