rebase/merge .zshrc commands

.zshrc

rebase_or_merge () {
  local branch=${1:-$(git config --get init.defaultBranch)}
  local remote=${$(git remote | grep '^upstream$'):-origin}

  git fetch $remote
  git $CMD $remote/$branch
}

# Usage: merge <branch>
merge () {
  CMD=merge rebase_or_merge
}

# Usage: rebase <branch>
rebase () {
  CMD=rebase rebase_or_merge
}