just some test message
leans the concept of untracked, tracked, unchanged, changed, staged and
committed.

leans how to uses diff and its concept.
leans the concept of skipping stage area.
leans about concept of skipping stage area.
learns about the concept of git rm
restore to previous version
let's do it!

and also leans the git commit -amend command

see whether git commit --amend is recursive
do some hot fix, please.
some work happend on master branch
Merge branch 'b1.test'