chore: split everything up into their own files & add a bunch of tests

tests/utils.nix

@@ -0,0 +1,36 @@
+{
+  lib,
+  pkgs,
+  ...
+}: let
+  cilib = import ./../lib {inherit lib pkgs;};
+in {
+  nixtest.suites."Utils" = {
+    pos = __curPos;
+    tests = [
+      {
+        name = "commitAndPushFiles";
+        type = "script";
+        script = let
+          inherit (cilib) utils;
+          job = builtins.toFile "test" (
+            builtins.unsafeDiscardStringContext (
+              builtins.toJSON (
+                utils.commitAndPushFiles {
+                  message = "hello world";
+                  files = ["a.md" "b.txt"];
+                } {}
+              )
+            )
+          );
+        in
+          # sh
+          ''
+            export PATH=${lib.makeBinPath [pkgs.gnugrep]}
+            grep -q 'git commit -m \\"hello world\\"' ${job}
+            grep -q 'git add a.md b.txt' ${job}
+          '';
+      }
+    ];
+  };
+}