MEPX
Chapter 7 of 10All chapters
  1. 1Reading is the job
  2. 2Getting oriented
  3. 3Understanding a function
  4. 4Following state
  5. 5Recognising shapes
  6. 6Reading for trouble
  7. 7Using history
  8. 8Tests as documentation
  9. 9Taking notes
  10. 10Reading in review

Chapter 7 of 10

Using history

The code is a record of decisions.

Blame and log

git blame shows which commit last touched a line, and the message often explains the line that looks pointless. A strange condition usually has an incident behind it.

  • Look at the whole commit, not just the line: context is in the neighbours.
  • A line changed many times is a line people keep getting wrong.

Chesterton's fence

Before removing something you do not understand, find out why it was put there. Code that looks redundant is often load-bearing in a way nobody documented.