Trimming old Commits from Github

Im sure there is a much more efficient way of doing this, but I had to remove about 2000 commits from my repo.. this is how I achieved it.

Step 1: Identify the commit to be your new root

For this I simply looked in Github, at the commit history. And I selected this one (my first commit)

Gihub Commit

My commit was 295c4c6ece076396eef2d8477d768d4c255b14b9

Step 2: Clone and Trim all commits before

Check out a new branch with that commit hash

git checkout -b oldroot 295c4c6ece076396eef2d8477d768d4c255b14b9
git write-tree 

Note the output. Mine was 00fb96df77166974bacb5bfa16e28cbd1baf8fbd Take that new, add a commit message and commit-tree

git commit-tree -m "New History Rebase" 00fb96df77166974bacb5bfa16e28cbd1baf8fbd

Note the output again. Mine was 64e19740fb1b78d89c3ca3bf6cf60d124caf7c14 Checkout a new branch with this new root, and rebase into master.

git checkout -b newroot 64e19740fb1b78d89c3ca3bf6cf60d124caf7c14
git rebase --onto newroot oldroot master
# repeat for other branches than master that should use the new initial commit
git checkout master
git branch -D oldroot
git branch -D newroot

Step 3: Actully trim

Danger Notice: Make sure you have a backup!!!

Execute this:

git gc 

Step 4: Clean up the remote (github)

Im sure there is a much better way to do this…. but this is what worked for me.

git checkout newmaster
git push --set-upstream origin newmaster

Now we need to go to github and change the default branch away from master (to new master). If you dont do this, the remote delete will be rejected. Gihub Commit

Once done…we delete the remote master (and local master); then create a new master branch.

git push origin --delete master
git branch -D master
git checkout -b master
git push --set-upstream origin master

Now go back to where you were on github before; and change the default back to master again; then we remove the newmaster branch.

git push origin --delete newmaster
git branch -D newmaster

And done… all old commits before your hash should be removed, and the branches cleaned up.