fix(git): use the correct alias section name && add unstage alias

Author: WilliamHsieh

home/git.nix

@@ -32,11 +32,12 @@
         name = dotfiles.fullname;
         email = dotfiles.email;
       };
-      aliases = {
+      alias = {
         undo = "reset HEAD@{1}";
         lg = "log --pretty=format:'%C(red)%h %C(blue)<%an> %C(green)%cs (%cr)  %C(reset)%s %C(auto)%d' --abbrev-commit --graph";
         pushf = "push --force-with-lease";
         review = /* bash */ ''!f() { nvim +"DiffviewFileHistory --range=''${1:-master}.."; }; f'';
+        unstage = "reset HEAD --";
       };
       init.defaultBranch = "master";
       core = {