Pitfalls in Git Staging Area: How to Undo Accidental `add` of Files?

When an unintended file (e.g., temporary files) is added to the staging area using `git add`, it can be undone with `git reset`. The staging area acts as a temporary中转站 (transit station), where `git add` copies snapshots of files from the working directory. It is essential to understand its relationship with the working directory and the local repository (HEAD). Core command: `git reset HEAD <filename>` reverts the specified file version in the staging area to match the local repository (undoing the `git add` for that file), while preserving the working directory content. If `git add .` was mistakenly executed, use `git reset HEAD` to undo all staged files. To remove incorrect content from the working directory, `git checkout -- <filename>` can restore it to the staging area or the most recent commit version. Key distinction: `reset` only undoes staging area operations, while `checkout` restores working directory content. Remember: Use `git reset HEAD <filename>` (for individual files) or `git reset HEAD` (for all files) to undo staging. `checkout` may be necessary to handle working directory changes when required.