20

I need a commit to no longer be in the git database of commits. I need to be able to remove commit abc123... such that git checkout abc123... returns error: pathspec 'abc123...' did not match any file(s) known to git.

The QA Delete commits from a branch in Git answers this partially, as in how to remove references to a commit from the HEAD, but it doesn't cover finding all of the branches a commit is present in nor does it cover expiring and purging the commit once it has been made a dangling commit.

How would I achieve this?

Didier L
  • 18,905
  • 10
  • 61
  • 103
Ethan Reesor
  • 2,090
  • 1
  • 23
  • 40
  • What was done in the commit? Do you want that to still happen, but in the following commit? Or did it, e.g. add a file you want to completely remove? Either way, you'll have to use some form of history rewriting. – Matthew Flaschen Jun 30 '12 at 03:59
  • I found [this useful post](https://wincent.com/wiki/Obliterating_a_Git_commit) by searching the web for "git obliterate". – Adam Monsen Jun 30 '12 at 07:08
  • 2
    This is not a duplicate of [Delete commits from a branch in Git](https://stackoverflow.com/questions/1338728/delete-commits-from-a-branch-in-git). That question asks, "How can I remove a commit from a branch?" My question is, "How can I entirely remove a commit from Git's database?" – Ethan Reesor Mar 13 '22 at 17:28
  • @EthanReesor You’re absolutely correct. I don’t understand why it wasn’t opened again four months ago. Being able to selectively remove objects—not to nuke everything unreachable but just the object that you want to remove—would be useful. – Guildenstern May 21 '23 at 12:26

2 Answers2

18

  1. List all branches that contain the commit:

    git branch --contains COMMITSHA

  2. Remove commit from these branches:

    git checkout BRANCH
git rebase -i COMMITSHA^
# delete line with commit and save

    If a changed branch is tracked in any remote, push it there with override:

    git push --force REMOTE BRANCH

    e.g:

    git push --force origin master

    (Note that, depending on your development process, the commit may appear in untracked remote branches as well.)

  3. Purge the commit, so it can not be restored from your local repo:

    git reflog expire --all BRANCH1 BRANCH2 # list all branches you changed
git prune --expire now

    Note that you must also run this command on all remote repositories that had this commit. If you have no access to the remote repo, you have to cross your fingers — commit will eventually expire by itself and will be purged by git gc.

    Be warned that above commands will remove all dangling objects from Git repo and all the history of branch changes — so you wouldn't be able to restore (by non-forensic means) anything lost prior to its run.

  4. Tell all collaborators to fetch changed branches and update any work they might have based on them. They should do as follows:

    git fetch REMOTE

    For each branch that is based on a branch you changed above (including the branch itself if they have it locally):

    git checkout BRANCH
git rebase REMOTE/BRANCH
git reflog expire --all BRANCH

    After they're done:

    git prune --expire now
Alexander Gladysh
  • 39,865
  • 32
  • 103
  • 160
1
  1. Make sure that no refs need that commit (reset back to before it, or rebase it out)
  2. Delete the object from .git/objects (it'll be in a folder named after the first two characters of the hash, and the filename will be the rest of the hash).

Note, however, that if you pushed this commit to a public repository, removing it locally won't remove it from the remote.

Amber
  • 507,862
  • 82
  • 626
  • 550
  • Ouch. It is probably not a good idea to touch `.git/objects` manually — given that there is `git prune` command for this case. – Alexander Gladysh Jun 30 '12 at 06:52
  • @AlexanderGladysh `git prune` involves more steps to make sure the object is actually removed (such as making sure to clear out the reflogs, et cetera). Removing the object file directly doesn't require those steps and is generally safe as long as you're not depending on the commit for anything. – Amber Jun 30 '12 at 06:54
  • `git reflog expire --all BRANCH` should do that, no? – Alexander Gladysh Jun 30 '12 at 07:24
  • Step 2 here is only safe here if you've performed step 1 successfully, and **no** refs need that commit; but you didn't give any instructions on how to be **sure** of that. – IMSoP Apr 19 '22 at 09:20
  • This looks like a complete solution if the commit was recently made. But it won’t work if the object has been moved to a packfile. – Guildenstern May 21 '23 at 11:57