I sort of got the hang of both deleting code, refactoring code and also adding a lot of code.
At work, we all agreed that before we change or remove code from another dev that is still with the company we should ask for a confirmation.
This works really well both because we are a small team and there is a lot of undocumented code and decision made without leaving a trail. Some snippets look like "magic" and therefore changing something might have an unintended effect. This unwritten rule assumes somehow that solid logic had some reasoning behind it, but lack of documentation makes it hard to follow or understand.
Worth to mention that I am talking only about changes that touch on logic and algorithms, not about small fixes and refactoring.
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