undo shortcut

.gitconfig

@@ -5,6 +5,7 @@
 [alias]
     lg = log --color --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit
     cu = "!git branch --merged | grep -v '\\*' | grep -v master | xargs -n 1 git branch -d"
+    undo = reset HEAD~
 [commit]
 	gpgsign = true
 [core]