Added git update shortcut

update fetches from the upstream remote and then rebases
upstream branch onto the current branch.

git/gitconfig.symlink

@@ -44,6 +44,9 @@
 
     cleanup = "!git remote prune origin && git gc && git clean -df && git stash clear"
 
+    # rebase the current branch with changes from upstream remote
+    update = !git fetch upstream && git rebase upstream/`git rev-parse --abbrev-ref HEAD`
+
     # grep commands
 
     # 'diff grep'