This paper presents Sanitizer, a tool for maintaining a student assignment and its reference solution in a single Git repository. The solution to the assignment is kept on its own branch, and is annotated with a simple inline markup. Based on this markup, Sanitizer removes files or parts of them, and commits the result to the student branch that can then be safely distributed to students. This provides a consistent workflow for developing assignments and their solutions together, avoiding the problem of drift between assignment and solutions over time, and simplifying the sharing of solutions with other teachers.