git diff
git diff [--staged] [a] [b]
Risk: Safe
What it does
Shows the changed lines. Red removed, green added.
When to use it
Before you add or commit.
Example
$ git diffChanges not in the box yet.
$ git diff --stagedChanges in the box.
$ git diff HEAD~2 HEADBetween two commits.
Learn it in: Spot the difference · Official docs