readme.md

init

mkdir proj
cd proj
git init

config

git config user.name 'username'
git config user.email 'username@douban.com'

create

echo 'test' > first
git hash-object -w first # got a sha1 as s1
git update-index --add --cacheinfo 100644 s1 first
git write-tree # got a sha1 as s2
git commit-tree s2 -m " "# got a sha1 as s3
git -c core.logAllRefUpdates=True update-ref refs/heads/master s3

edit

echo 'test' > second
git hash-object -w first # got a sha1 as s1
git update-index --add --cacheinfo 100644 s1 second
git write-tree # got a sha1 as s2
git commit-tree s2 -p master -m " " # got a sha1 as s3
git -c core.logAllRefUpdates=True update-ref refs/heads/master s3