Fix "cannot 'squash' without a previous commit" for Git

Suppose you create a new codebase and you have only 2 commits. Now you want to combine the 2nd commit to the 1st commit with this command.

git rebase -i HEAD~1

However, Git cannot perform that and it returns an error message like this.

error: cannot 'squash' without a previous commit

For this case, you should try this.

git rebase -i --root