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GitHub is a powerful tool for developers, but managing commit histories can sometimes become daunting, especially if you need to delete a commit. This guide will walk you through various scenarios to help you understand how to delete or amend commits in GitHub effectively. From simple tweaks like changing a commit message to more complex operations like rewriting history, this comprehensive tutorial will serve as your go-to resource. We’ll cover uncommitted changes, local and pushed commits, merge commits, and even discuss how to responsibly rewrite published history.
First step
The first step when attempting to delete a commit in GitHub is to identify what you want to achieve. Are you dealing with uncommitted changes, or have you already pushed the commit? Understanding your current state and your desired outcome will dictate the steps you need to follow.
Open your terminal or command line interface and navigate to the Git repository where the problematic commit exists. Making sure your working directory is clean before performing any operations can prevent further complications.
Are you trying to find that which is lost or fix a change that was made?
Do you need to recover something lost or amend a change? Finding lost commits often involves using `git reflog` to view your commit history, including commits that have been orphaned. If it’s a fix you need, determining whether it’s related to content or just the commit message will shape your approach.
Use `git log` to carefully examine the history and understand the nature of your commit. This helps you identify which commits need attention and whether they involve changes to a file, directories, or simply the commit messages.
Have you committed?
If you haven’t yet committed, you’re in a better position to undo or amend changes. You can discard uncommitted changes easily without affecting the commit history of your project.
If changes are already committed, the complexity increases based on whether those commits are local or have been pushed to a remote repository.
Everything or just some things?
Are you looking to undo all your recent changes, or just specific parts? Identifying the scope of your amendments is crucial and often decides whether you need to reset, revert, or cherry-pick specific commits.
Depending on whether you want to undo specific changes or reset everything to a previous state, the approach will vary. Commands like `git reset` and `git revert` serve different purposes and should be chosen based on your specific requirements.
How to undo all uncommitted changes
To discard all uncommitted changes, the command `git reset –hard` is your best friend. This will reset your working directory to match the state of your last commit, discarding anything you’ve altered since then.
Remember, this action is irreversible, so make sure you definitely want to discard these changes before running the command.
How to undo some uncommitted changes
If you need to undo only specific changes, use `git checkout —
You can also use `git restore
Do you have a clean working directory?
Before making significant changes to your commit history, it’s essential to ensure that your working directory is clean. Use the command `git status` to confirm this.
If there are untracked or modified files, either commit or stash them before proceeding. This ensures you can revert back if something goes wrong during the process.
Have you pushed?
If you haven’t pushed the commit yet, altering or deleting it is a lot simpler. Local changes can be modified using commands like `git commit –amend` or `git reset` without affecting any collaborators.
If the commit has been pushed, particularly to a shared branch, proceed with caution as changing history can impact other users negatively.
Do you want to discard all unpushed changes on this branch?
To discard all unpushed commits and reset your branch to match the remote, use `git reset –hard origin/
This command will remove all local changes that are not reflected on the remote branch, aligning your local repository with the shared history.
Discarding all local commits on this branch
To discard only the local commits but keep staged and working directory changes, use `git reset –soft HEAD~
This way, the changes will remain staged but not committed, allowing you to adjust and recommit them as needed.
Replacing all branch history/contents
If you need to replace the entire branch’s history or contents, advanced commands like `git filter-branch` or the newer `git filter-repo` are necessary. These tools allow you to rewrite the history of an entire branch comprehensively.
While powerful, these commands can be dangerous if not used correctly. Make sure to read the documentation thoroughly and back up your repository before proceeding.
Is the commit you want to fix the most recent?
Fixing the most recent commit is straightforward. You can amend the last commit using `git commit –amend`. This command opens the editor, allowing you to change the commit message or modify the commit contents.
Just be cautious, as amending a commit changes its hash, meaning it effectively creates a new commit.
Do you want to remove or change the commit message/contents of the last commit?
To update the commit message, you use `git commit –amend` followed by a new commit message. To change the commit contents, stage the desired changes first and then amend the commit.
Run `git commit –amend -m “New Commit Message”` if you only want to change the message. If you need to change the contents, add the changes using `git add
Removing the last commit
To remove the last commit, use `git reset –hard HEAD~1`. This will delete the last commit from your history completely.
Be extremely cautious using this command as it will also discard any changes done in the last commit.
Updating the last commit’s contents or commit message
When updating the last commit’s content or message, use the amend option as discussed. First, stage new changes, then use `git commit –amend` to update the last commit.
For changing only the commit message, `git commit –amend -m “New Commit Message”` is adequate, allowing you to update the last commit’s message easily.
Do you want to remove an entire commit?
To remove an entire commit, you can use `git rebase` to rewrite history. Commands like `git rebase -i HEAD~N` where `N` is the number of commits can help you remove unwanted commits.
During the interactive rebase, you can choose to “drop” a commit, effectively removing it from history.
Removing an entire commit
If you’ve decided to remove a commit, be mindful of the changes it introduced. Using `git rebase -i` allows you to edit history and remove specific commits while keeping related commits intact.
This task can be complex if other commits depend on the one you are trying to remove, requiring caution and thorough review.
Do you want to remove/change/rename a particular file/directory from all commits during all of git’s history
If you need to remove or change a file across all commits, `git filter-branch` or `git filter-repo` is the way to go. These commands help rewrite the history by applying the desired changes across all commits.
Be cautious though, as this will change the commit hashes and can affect all collaborators working on the repository.
Is a merge commit involved?
Handling merge commits requires additional caution. If a merge commit contains changes from multiple parents, removing it can result in lost history.
Using `git revert -m 1
Changing a single commit involving only simple commits
Amending a single commit that does not involve merges can be done via `git rebase -i`, allowing you to drop, edit, or squash commits as needed.
This is generally straightforward but it’s essential to ensure no other work depends on the commit you are editing or discarding.
Changing a single commit involving a merge
When a merge commit needs alteration, it requires a more careful approach. Use `git revert -m` to create a new commit that undoes the changes from the merge, or use `rebase -i` with caution.
Interactive rebase in this case should be handled carefully to avoid conflicts. Manual editing during the rebase might be needed to solve conflicts.
Can you make a positive commit to fix the problem and what is the fix class?
Sometimes adding a new commit to fix a problem is simpler and less risky than deleting or rewriting existing commits. Identifying whether it’s a bug fix, a documentation update, or something else classifies the type of fix needed.
Makes sure the new commit message correctly references the problem and describes the fix to maintain a clear project history.
Making a new commit to fix an old commit
Creating a new commit to fix an old commit is often the safest route. Add the necessary changes, stage them, and commit with a message referencing the old commit, e.g., “Fix issue introduced in commit
These incremental fixes preserve history and make it clear what changes were made and why.
Making a new commit to restore a file deleted earlier
If you need to restore a file deleted in an earlier commit, use `git checkout
Stage and commit the restored file to bring it back to the working directory and project history.
Reverting an old simple pushed commit
If the commit is already pushed and you need to revert it, use `git revert
This approach is safe and preserves the project history by adding a new commit rather than removing an old one.
Reverting a merge commit
Reverting a merge commit can be tricky but is manageable. Use `git revert -m 1
This creates a new commit that undoes the changes from the merge commit without altering the commit history, reducing the risk of losing important history.
Rewriting an old branch with a new branch with a new commit
If you need to replace the entire history of a branch, create a new branch from the target point, apply your new commits, and then force-push (`git push -f`) the new branch to replace the old one.
This operation is drastic and should be used sparingly, particularly on branches that are shared with others.
I am a bad person and must rewrite published history
Rewriting published history is generally discouraged but sometimes unavoidable. Always communicate with your team about the changes and provide ample warning.
Use commands like `git rebase -i` or `git filter-branch` and know that force-pushing (`git push -f`) will be necessary to update the remote history.
I have lost some commits I know I made
Use `git reflog` to find lost commits. This command shows a log of all changes made to the local repository, even those that aren’t part of the current branch history.
Once identified, you can use `git checkout
Undoing the last few git operations affecting HEAD/my branch’s tip
To undo recent operations, `git reset` is useful. Use `git reset –hard HEAD~N` where `N` is the number of operations to undo.
This command will undo the last N commits, moving the HEAD to a previous state. Be cautious as this will discard recent changes.
Recovering from a borked/stupid/moribund merge
If a merge goes wrong, you can often recover using `git reset –merge ORIG_HEAD`. This command resets the branch to its state before the merge, allowing you to reattempt.
Alternatively, `git reflog` can help you find the state before the merge and checkout from that point to resolve the conflicts correctly.
Recovering from a borked/stupid/moribund rebase
To recover from a failed rebase, use `git rebase –abort` to stop the rebase process and return to the previous state. This discards the rebase changes and restores your branch to before you started the rebase.
If the rebase has already been completed and conflicts need resolution, `git reflog` can again be beneficial for finding a stable commit to reset or branch from.
Disclaimer
While the steps outlined in this guide are tried and tested, always remember to back up your repository before making significant changes. Rewriting history can have serious implications if not handled correctly.
When in doubt, consult the official Git documentation or seek assistance from more experienced colleagues.
Copyright
© 2023 Lucas Martin. All rights reserved. Redistribution or reproduction of this material without prior written permission is prohibited.
Thanks
Thank you for taking the time to read this guide. Special thanks to the open-source community for providing extensive resources and support.
Comments
If you have any questions, comments, or suggestions, please leave them below. Your feedback helps improve future guides and resources.
| Subheading | Summary |
|---|---|
| First step | Start by identifying your current state and the outcome desired. |
| Are you trying to find that which is lost or fix a change that was made? | Determine if you need to recover lost commits or amend a change. |
| Have you committed? | Check if changes are committed or still uncommitted to choose the right action. |
| Everything or just some things? | Decide whether you want to undo everything or specific parts. |
| How to undo all uncommitted changes | Use `git reset –hard` to discard all uncommitted changes. |
| How to undo some uncommitted changes | Use `git checkout — |
| Do you have a clean working directory? | Ensure a clean working directory using `git status` before making history changes. |
| Have you pushed? | Determine if the commit has been pushed to know whether you can safely amend it. |
| Do you want to discard all unpushed changes on this branch? | Use `git reset –hard origin/ |
| Discarding all local commits on this branch | Use `git reset –soft HEAD~ |
| Replacing all branch history/contents | Use advanced commands like `git filter-branch` or `git filter-repo` to replace branch history. |
| Is the commit you want to fix the most recent? | If so, use `git commit –amend` to update the recent commit. |
| Do you want to remove or change the commit message/contents of the last commit? | Amend the last commit using `git commit –amend -m “New Commit Message”` for message or add and amend for content change. |
| Removing the last commit | Use `git reset –hard HEAD~1` to remove the last commit completely. |
| Updating the last commit’s contents or commit message | Stage changes and use `git commit –amend` to update the last commit. |
| Do you want to remove an entire commit? | Use `git rebase -i HEAD~N` to interactively remove an entire commit. |
| Removing an entire commit | Use `git rebase -i` during interactive mode to drop a commit. |
| Do you want to remove/change/rename a particular file/directory from all commits during |
