how to delete all commit history in github?

I want to delete all commit history but keep the code in its current state because, in my commit history, there are too many unused commits.

How can I do it?

Is there any git command can do this?

git filter-branch ?
git rebase ?
... 

My code is hosted on github.com.

Deleting the .git folder may cause problems in your git repository. If you want to delete all your commit history but keep the code in its current state, it is very safe to do it as in the following:

1. Checkout

   git checkout --orphan latest_branch

2. Add all the files

   git add -A

3. Commit the changes

   git commit -am "commit message"

4. Delete the branch

   git branch -D main

5. Rename the current branch to main

   git branch -m main

6. Finally, force update your repository

   git push -f origin main

PS: this will not keep your old commit history around

If you are sure you want to remove all commit history, simply delete the .git directory in your project root (note that it's hidden). Then initialize a new repository in the same folder and link it to the GitHub repository:

git init
git remote add origin git@github.com:user/repo

now commit your current version of code

git add *
git commit -am 'message'

and finally force the update to GitHub:

git push -f origin master

However, I suggest backing up the history (the .git folder in the repository) before taking these steps!