How to remove file from historical commit with Git?

When working with Git, if you need to permanently remove a file from the commit history, you can use the git filter-branch command or third-party tools such as BFG Repo-Cleaner. I will explain both methods in detail:

Method 1: Using git filter-branch

1. Open the terminal: Begin by opening your command-line interface.

2. Navigate to the repository directory: Use the cd command to switch to your Git repository directory.

3. Execute the deletion command: Use the following command to remove the file.

   bash
   git filter-branch --force --index-filter \n   "git rm --cached --ignore-unmatch path to your file" \n   --prune-empty --tag-name-filter cat -- --all

   • --index-filter: Applies a filter to each commit.
   • "git rm --cached --ignore-unmatch path to your file": Removes the specified file.
   • --prune-empty: Eliminates commits that become empty due to file deletion.
   • --tag-name-filter cat: Processes tags.
   • --all: Applies changes to all branches and tags.

   For example, to remove the file named secret.txt, use:

   bash
   git filter-branch --force --index-filter \n   "git rm --cached --ignore-unmatch secret.txt" \n   --prune-empty --tag-name-filter cat -- --all

4. Push the changes: After completing the above steps, push the changes to the remote repository using:

   bash
   git push origin --force --all
   git push origin --force --tags

Method 2: Using BFG Repo-Cleaner

1. Download and run BFG: First, download and install BFG from the official website.

2. Backup your repository: Before proceeding, it is recommended to back up your repository.

3. Use BFG to remove the file:

   bash
   java -jar bfg.jar --delete-files "path to your file" your-repository-directory

   For example, to remove secret.txt, your command would be:

   bash
   java -jar bfg.jar --delete-files secret.txt my-repo.git

4. Continue cleanup and push:

   bash
   cd your-repository-directory
   git reflog expire --expire=now --all && git gc --prune=now --aggressive
   git push

When using these tools, ensure you fully understand their functionality and potential risks. Removing a file from the commit history alters your project history, which may impact the repository state of other collaborators. Additionally, once changes are pushed, all historical versions will be rewritten, potentially leading to data loss.