You can learn git object and git internal by git-object-trainer.
git-object-trainer dosen't allow you to Porcelain git commands(add, commit, show, diff, checkout, tag, log, diff). You have to use Plumbing git commands(hash-object, cat-file, update-index, write-tree) instead of Porcelain git commands.
If you exec git add, git-object-trainer teach you how to construct git add with Plumbing git command.
go get github.com/sonatard/git-object-trainer/Add alias to your .bash_profile
- .bash_profile
alias git=git-object-trainer
$ git add .
Error: Exec following commands instead of git add
Basic way
# 1. Create . objects
$ git hash-object -w .
[FILE-HASH-STRING]
# 3. Check created object
$ git cat-file -p [FILE-HASH-STRING]
[FILE STRINGS]
# 4. Add or update file to staging area
## 4.1 add
$ git update-index --add --caechinfo 10644 [FILE-HASH-STRING] .
## 4.2 update
$ git update-index --caechinfo 10644 [FILE-HASH-STRING] .
# 5. Create tree
$ git write-tree
[TREE-HASH-STRING]
Remember [TREE-HASH-STRING] for commit
# 6. Check tree object
$ git cat-file -p [TREE-HASH-STRING]
[PERMISSION] blob [HASH] .
Easy way. You need not to remember [FILE-HASH-STRING]
# 1. Create tree
$ git write-tree
[TREE-HASH-STRING]
Remember [TREE-HASH-STRING] for commit
# 2. Add or update file to staging area
## 4.1 add
$ git update-index --add .
## 4.2 update
$ git update-index .
# 6. Check tree object
$ git cat-file -p [TREE-HASH-STRING]
[PERMISSION] blob [HASH] .