. /t/prompt/prompt 
test -d demo && rm -rf demo/
test -d ../demo && cd .. && rm -rf demo/ 
clear
mkdir demo
cd demo
git init
### all git info is inside ().   "M" - indicate master
echo "1st line" > file
###   intersting files are shown and colored according to git state
###   red - modified,  green - added to index, blue - untracked, 
git add file
touch  untracked-file
rm     untracked-file
git commit -m "1st line"  file
git checkout -b test
echo 'added 2nd line in test' >> file 
git add file 
echo "2nd file" > file2
git add file2
echo 'added 3nd line in file, still in test' >> file 
git add file
git commit -m "2nd and 3rd lines"
git checkout master
cat file 
echo 'now added 2nd line in master' >> file 
git add file
git commit -m v2
git merge test
###  magenta - operation in progress (merge, rebase, ...)
git-cat-file -p test:file > file
git add file 
git commit -m merged