zplug: add module

This adds initial support for the zsh package manager "zplug".

PR #1105

tests/modules/programs/zplug/default.nix

@@ -0,0 +1 @@
+{ zplug-modules = ./modules.nix; }

tests/modules/programs/zplug/modules.nix

@@ -0,0 +1,48 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  config = {
+    programs.zsh = {
+      enable = true;
+      zplug = {
+        enable = true;
+        plugins = [
+          {
+            name = "plugins/git";
+            tags = [ "from:oh-my-zsh" ];
+          }
+          {
+            name = "lib/clipboard";
+            tags = [ "from:oh-my-zsh" ''if:"[[ $OSTYPE == *darwin* ]]"'' ];
+          }
+        ];
+      };
+    };
+
+    nixpkgs.overlays = [
+      (self: super: {
+        zsh = pkgs.writeScriptBin "dummy-zsh" "";
+        zplug = pkgs.writeScriptBin "dummy-zplug" "";
+      })
+    ];
+
+    nmt.script = ''
+      assertFileRegex home-files/.zshrc \
+        '^source ${builtins.storeDir}/.*zplug.*/init\.zsh$'
+
+      assertFileContains home-files/.zshrc \
+        'zplug "plugins/git", from:oh-my-zsh'
+
+      assertFileContains home-files/.zshrc \
+        'zplug "lib/clipboard", from:oh-my-zsh, if:"[[ $OSTYPE == *darwin* ]]"'
+
+      assertFileRegex home-files/.zshrc \
+        '^zplug install$'
+
+      assertFileRegex home-files/.zshrc \
+        '^zplug load$'
+    '';
+  };
+}