# M02-L05 exercise — Challenge: save only what belongs

**Start:** M02-L01–04; disposable CP01 practice repository with an existing baseline.

In the disposable repository, create `build-note.tmp` containing “Harmless generated teaching output.” Make a useful README clarification and deliberately stage both files. Confirm a baseline commit already exists.

Inspect state, unstage only the temporary file, add an exact `.gitignore` entry, and review the final staged snapshot. Commit the intended README/ignore changes. Submit before/after state, final commit summary, and a paragraph distinguishing unstage, discard, and ignore. Preserve the harmless temporary file long enough to demonstrate that unstaging did not delete it.