What to look at before editing: history as a source of reasons

Before changing code it helps to find out why it is the way it is. History answers that better than comments do: it shows what was changed, when, and with what explanation.

git log --oneline -10          recent changes
git log -p file               the history of one file
git show COMMIT               what exactly was in a commit
git blame file                who wrote a line and when

Some commits in this project have long messages that dig into the reason. That is deliberate: a line of code can be read, but why it was written that way can be found nowhere except the history.