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

lib/jobRun.nix

@@ -0,0 +1,48 @@
+{
+  lib,
+  pkgs,
+  ...
+}: let
+  cilib = import ./. {inherit lib pkgs;};
+  inherit (cilib.helpers) filterJobVariables;
+in {
+  mkJobRun = {
+    key,
+    job,
+    jobDeps,
+  }: let
+    variablesWithoutStorePaths = filterJobVariables false job;
+    variableExports = lib.concatLines (
+      lib.mapAttrsToList (name: value: "export ${name}=\"${value}\"") variablesWithoutStorePaths
+    );
+    sandboxHelper = pkgs.writeShellScriptBin "gitlab-ci-job-sandbox-helper" (builtins.readFile ./sandbox_helper.sh);
+    actualJobScript = pkgs.writeShellScript "gitlab-ci-job:${key}:raw" ''
+      # set up deps and environment variables containing store paths
+      . ${jobDeps}
+      # normal environment variables
+      ${variableExports}
+      # run before_script, script and after_script
+      echo -e "\e[32mRunning before_script...\e[0m"
+      set -x
+      ${lib.concatLines (job.before_script or [])}
+      { set +x; } 2>/dev/null
+      echo -e "\e[32mRunning script...\e[0m"
+      set -x
+      ${lib.concatLines job.script}
+      { set +x; } 2>/dev/null
+      echo -e "\e[32mRunning after_script...\e[0m"
+      set -x
+      ${lib.concatLines (job.after_script or [])}
+      { set +x; } 2>/dev/null
+    '';
+  in
+    # this way the sandbox helper just needs to be built once
+    pkgs.writeShellScriptBin "gitlab-ci-job:${key}" ''
+      exec ${lib.getExe sandboxHelper} ${actualJobScript} $@
+    ''
+    // {
+      passthru = {
+        inherit jobDeps actualJobScript;
+      };
+    };
+}