When working on files where you want to commit specific line changes into separate commits, there is a way to individually select lines of the changes that you want to commit.
Use:
git add -p
Git diff on its own lets you view changes between your HEAD and the current unstaged state.
To view changes of staged changes (but not committed), use:
git diff --cached
In order to save time, in my personal ~/.gitconfig, I’ve added an alias:
[alias]
changes = diff --cached
Reference: [1] How can I commit only part of a file in git [2] How do I show the changes which have been staged