Some day you or a collaborator may accidentally commit sensitive data, such as a password or SSH key, into a Git repository. Although you can remove the file from the latest commit with git rm, the file will still exist in the repository's history. Fortunately, there are other tools that can entirely remove unwanted files from a repository's history. This article will explain how to use two of them: git filter-branch and the BFG Repo-Cleaner.

Danger: Once you have pushed a commit to GitHub, you should consider any data it contains to be compromised. If you committed a password, change it! If you committed a key, generate a new one.

This article tells you how to make commits with sensitive data unreachable from any branches or tags in your GitHub repository. However, it's important to note that those commits may still be accessible in any clones or forks of your repository, directly via their SHA-1 hashes in cached views on GitHub, and through any pull requests that reference them. You can't do anything about existing clones or forks of your repository, but you can permanently remove all of your repository's cached views and pull requests on GitHub by contacting GitHub support.

Purging a file from your repository's history

Using the BFG

The BFG Repo-Cleaner is a faster, simpler alternative to git filter-branch for removing unwanted data. For example, to remove your file with sensitive data and leave your latest commit untouched), run:

bfg --delete-files YOUR-FILE-WITH-SENSITIVE-DATA

To replace all text listed in passwords.txt wherever it can be found in your repository's history, run:

bfg --replace-text passwords.txt

See the BFG Repo-Cleaner's documentation for full usage and download instructions.

Using filter-branch

To illustrate how git filter-branch works, we'll show you how to remove your file with sensitive data from the history of your repository and add it to .gitignore to ensure that it is not accidentally re-committed.

  1. If you don't already have a local copy of your repository with sensitive data in its history, clone the repository to your local computer.

    git clone https://github.com/YOUR-USERNAME/YOUR-REPOSITORY
    Initialized empty Git repository in /Users/YOUR-FILE-PATH/YOUR-REPOSITORY/.git/
    remote: Counting objects: 1301, done.
    remote: Compressing objects: 100% (769/769), done.
    remote: Total 1301 (delta 724), reused 910 (delta 522)
    Receiving objects: 100% (1301/1301), 164.39 KiB, done.
    Resolving deltas: 100% (724/724), done.
    
  2. Navigate into the repository's working directory.

    cd YOUR-REPOSITORY
    
  3. Run the following command, replacing PATH-TO-YOUR-FILE-WITH-SENSITIVE-DATA with the path to the file you want to remove, not just its filename. These arguments will:

    • Force Git to process, but not check out, the entire history of every branch and tag
    • Remove the specified file, as well as any empty commits generated as a result
    • Overwrite your existing tags
      $ git filter-branch --force --index-filter \
      'git rm --cached --ignore-unmatch PATH-TO-YOUR-FILE-WITH-SENSITIVE-DATA' \
      --prune-empty --tag-name-filter cat -- --all
      > Rewrite 48dc599c80e20527ed902928085e7861e6b3cbe6 (266/266)
      > Ref 'refs/heads/master' was rewritten
      

    Note: If the file with sensitive data used to exist at any other paths (because it was moved or renamed), you must run this command on those paths, as well.

  4. Add your file with sensitive data to .gitignore to ensure that you don't accidentally commit it again.

    $ echo "YOUR-FILE-WITH-SENSITIVE-DATA" >> .gitignore
    $ git add .gitignore
    $ git commit -m "Add YOUR-FILE-WITH-SENSITIVE-DATA to .gitignore"
    > [master 051452f] Add YOUR-FILE-WITH-SENSITIVE-DATA to .gitignore
    >  1 files changed, 1 insertions(+), 0 deletions(-)
    
  5. Double-check that you've removed everything you wanted to from your repository's history, and that all of your branches are checked out.

  6. Once you're happy with the state of your repository, force-push your local changes to overwrite your GitHub repository, as well as all the branches you've pushed up:

    git push origin --force --all
    Counting objects: 1074, done.
    Delta compression using 2 threads.
    Compressing objects: 100% (677/677), done.
    Writing objects: 100% (1058/1058), 148.85 KiB, done.
    Total 1058 (delta 590), reused 602 (delta 378)
    To https://github.com/YOUR-USERNAME/YOUR-REPOSITORY.git
     + 48dc599...051452f master -> master (forced update)
    
  7. In order to remove the sensitive file from your tagged releases, you'll also need to force-push against your Git tags:

    git push origin --force --tags
    Counting objects: 321, done.
    Delta compression using up to 8 threads.
    Compressing objects: 100% (166/166), done.
    Writing objects: 100% (321/321), 331.74 KiB | 0 bytes/s, done.
    Total 321 (delta 124), reused 269 (delta 108)
    To https://github.com/YOUR-USERNAME/YOUR-REPOSITORY.git
     + 48dc599...051452f master -> master (forced update)
    
  8. Tell your collaborators to rebase, not merge, any branches they created off of your old (tainted) repository history. One merge commit could reintroduce some or all of the tainted history that you just went to the trouble of purging.

  9. After some time has passed and you're confident that git filter-branch had no unintended side effects, you can force all objects in your local repository to be dereferenced and garbage collected with the following commands (using Git 1.8.5 or newer):

    git for-each-ref --format='delete %(refname)' refs/original | git update-ref --stdin
    git reflog expire --expire=now --all
    git gc --prune=now
    Counting objects: 2437, done.
    Delta compression using up to 4 threads.
    Compressing objects: 100% (1378/1378), done.
    Writing objects: 100% (2437/2437), done.
    Total 2437 (delta 1461), reused 1802 (delta 1048)
    

    Note that you can also achieve this by pushing your filtered history to a new or empty repository and then making a fresh clone from GitHub.

Avoiding accidental commits in the future

There are a few simple tricks to avoid committing things you don't want committed:

  • Use a visual program like GitHub Desktop or gitk to commit changes. Visual programs generally make it easier to see exactly which files will be added, deleted, and modified with each commit.
  • Avoid the catch-all commands git add . and git commit -a on the command line—use git add filename and git rm filename to individually stage files, instead.
  • Use git add --interactive to individually review and stage changes within each file.
  • Use git diff --cached to review the changes that you have staged for commit. This is the exact diff that git commit will produce as long as you don't use the -a flag.

Further reading