Why doesn't git commit -a add new files?

Question

I\'m a bit new to git, and I fail to understand why git commit -a only stages changed and deleted files but not new files.

Can anyone explain why is it

Answer 1

I suggest another solution: using git commit --interactive -m "your commit message" will show you this menu

*** Commands ***
  1: [s]tatus     2: [u]pdate     3: [r]evert     4: [a]dd untracked
  5: [p]atch      6: [d]iff   7: [q]uit   8: [h]elp

allowing you to check status, add untracked files and so on using simple keystrokes.