How do I make Git forget about a file that was tracked, but is now in .gitignore?

To make Git stop tracking a file that is now in .gitignore but was previously tracked, you need to remove it from Git’s index (staging area) while keeping the file in your working directory. Here’s how to do it:

Steps

1. Add the file to .gitignore (if not already done):

   echo "filename" >> .gitignore  # Add the file to .gitignore
   git add .gitignore             # Commit the updated .gitignore
   git commit -m "Update .gitignore to exclude filename"

2. Remove the file from Git’s tracking (keeps the file locally):

   git rm --cached <file-path>    # Remove from Git's index but keep the file locally

3. Commit the change:

   git commit -m "Stop tracking <file-path>"

Example

Suppose you want to stop tracking logs/error.log and have added it to .gitignore:

git rm --cached logs/error.log
git commit -m "Remove logs/error.log from tracking"

Remove All Files Listed in .gitignore

If multiple files are listed in .gitignore and you want to untrack all of them:

git rm -r --cached .  # Remove all files from Git's index
git add .             # Re-add files, respecting .gitignore
git commit -m "Untrack files listed in .gitignore"

Key Notes

• File History: The file will still exist in Git’s history (previous commits). To purge it entirely, use tools like git filter-repo or BFG Repo-Cleaner.
• Collaborators: After you push the commit, others must run git pull to update their local repositories.
• File Retention: The --cached flag ensures the file stays in your working directory.

Why This Works

• git rm --cached removes the file from Git’s tracking (index) but leaves it in your working directory.
• .gitignore prevents Git from re-adding the file in future operations.

By following these steps, Git will “forget” the file while keeping it on your machine.