Git Objects

echo 'zqw' | git hash-object -w --stdin
# 3670911e6f6449df03f225ee1efb5acb8bfd4bc7

find .git/objects -type f
# .git/objects/36/70911e6f6449df03f225ee1efb5acb8bfd4bc7

git cat-file -p 3670911e6f6449df03f225ee1efb5acb8bfd4bc7
# zqw

####################

echo 'version 1' > ver.txt

git hash-object -w ver.txt
# 83baae61804e65cc73a7201a7252750c76066a30

find .git/objects -type f
# .git/objects/83/baae61804e65cc73a7201a7252750c76066a30

git cat-file -p  83baae61804e65cc73a7201a7252750c76066a30
# version 1

####################

git cat-file -t 3670911e6f6449df03f225ee1efb5acb8bfd4bc7
# blob

git update-index --add new.txt

####################

git write-tree
4873235733fd7a44f2c3e73937dd09e064cbac53

####################

echo 'first commit' | git commit-tree 4873235
0b74f629a3b25a22821634bc34cdd3077256ce39

####################

git cat-file -p 0b74f629a3b25a22821634bc34cdd3077256ce39
  tree 4873235733fd7a44f2c3e73937dd09e064cbac53
  author shooter <shooter@bitcoin.org> 1520676818 +0800
  committer shooter <shooter@bitcoin.org> 1520676818 +0800

  first commit

git log --stat 0b74f6
commit 0b74f629a3b25a22821634bc34cdd3077256ce39
Author: shooter <shooter@bitcoin.org>
Date:   Sat Mar 05 08:13:38 2017 +0800

    first commit

 new.txt | 0
 1 file changed, 0 insertions(+), 0 deletions(-)

Git 如何存储对象

通过 Ruby 脚本语言存储一个 git blob 对象

require 'digest'
require 'zlib'

content = "what is up, doc?"

header = "blob #{content.length}\0"
# => "blob 16\u0000"

store = header + content
# => "blob 16\u0000what is up, doc?"

sha1 = Digest::SHA1.hexdigest(store)
# => "bd9dbf5aae1a3862dd1526723246b20206e5fc37"

sha1[0,2]
# => "bd"

sha1[2,38]
# => "9dbf5aae1a3862dd1526723246b20206e5fc37"

zlib_content = Zlib::Deflate.deflate(store)
# => "x\x9CK\xCA\xC9OR04c(\xCFH,Q\xC8,V(-\xD0QH\xC9O\xB6\a\x00_\x1C\a\x9D"

path = '.git/objects/' + sha1[0,2] + '/' + sha1[2,38]
# => ".git/objects/bd/9dbf5aae1a3862dd1526723246b20206e5fc37"

FileUtils.mkdir_p(File.dirname(path))
# => [".git/objects/bd"]

File.open(path, 'w') { |f| f.write zlib_content }
# => 32

---

参考:

https://git-scm.com/book/en/v2/Git-Internals-Git-Objects