Git stores data in 3 main structures: the working directory, the staging area (index), and local repository. The working directory contains files that are currently being edited. The staging area stores files that will go into the next commit. The local repository stores the commits and the relationships between them. Git uses hashes to uniquely identify content in its database. Files in the working directory and staging area are tracked and stored as blobs in the local database. Blobs, trees, and commits make up the core git objects. Commits capture snapshots and link to the previous commit. The basic Git workflow involves making changes to files in the working directory, staging them, and committing. Commands like git diff, git checkout, and

1. Git
Git Data Model & Local Workflow
Liu Lin

2. Git Data Model

3. C1 C2 C3 C4 C6
Working
Directory
Stage
(index)
master
HEAD
files to go in next commit
commit object
current branch
reference to current branch
maint
another branch

4. How git stores your data?

5. Working
Directory
Stage
(index)
Local Repo
blob: size
This is the first line
6ccdfb
blob: size
This is the first line
This is the second line
60ed415
File: size
This is the first line
a.file
File: size
This is the first line
This is the second line
a.file
Hash Filename
6ccdfbd a.file
Hash Filename
60ed415 a.file

6. Working
Directory
Stage
(index)
Local Repo
blob: size
This is the first line
This is the second line
File: size
This is the first line
This is the second line
a.file
Hash Filename
6ccdfbd a.file
Hash Filename
60ed415 a.file
tree
blob: 60ed415 a.file
commit
tree: 0518ac a.file

7. ❖ Blob
blob
“version 1”
a.txt File
“version 1”

8. ❖ Tree
new.txt
fa49b0
“new file”
83baae
“version1”
d8329f
tree
3c4e9
tree
a.txt
dir

9. First commit
tree
“new file”
fa49b0
fa49b0
fdf4fc
Second commit
cac0ca
tree
“Version 1”
tree
3c4e9
d8329f
83baae
new.txt dir
a.txt
❖ Commit

10. Where git stores your data?

11. Git Repo
HEAD
config
index
objects
logs
refs heads
master
maint
60ed41
ed489
Hash Filename
60ed415 a.file
blob: size
This is the first line
This is the second line
ref: refs/heads/master
60ed41

12. How to see the git object?

13. git cat-file blob 60ed41
blob: size
This is the first line
This is the second line
git ls-files --stage
Hash Filename
60ed415 a.file
git ls-tree bf9cff
tree: size
blob: 60ed415 a.file
git cat-file commit ed489
commit: size
tree: bf9cff
parent: da985
the second commit

14. Git Local Workflow

15. Working
Directory
Stage
(index)
Local Repo
add commit
commit -a

16. Working
Directory
Stage
(index)
Local Repo
checkout HEAD
checkout
reset
reset --hard HEAD

17. Git Diff

18. ❖ git diff
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
fix
git diff
master
HEAD
git diff —cached

19. ❖ git diff
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
fix master
HEAD
git diff HEADgit diff fix
git diff C3 C4

20. Git Checkout

21. How to checkout file?

22. C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”
❖ git checkout C4 a.file

23. ❖ git checkout C4 a.file
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
-“the C5 commit line”
a.file
a.file
“the C4 commit line”
-“the C5 commit line”

24. How to checkout commit?

25. ❖ git checkout C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”

26. ❖ git checkout C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
-“the C5 commit line”
a.file
“the C4 commit line”
-“the C5 commit line”

27. How to checkout branch?

28. ❖ git checkout fix
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”
fix

29. ❖ git checkout fix
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
-“the C5 commit line”
fix
a.file
“the C4 commit line”
-“the C5 commit line”

30. Git Reset

31. How to reset file?

32. ❖ git reset C4 a.file
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”

33. ❖ git reset C4 a.file
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
-“the C5 commit line”
“the C4 commit line”
“the C5 commit line”
a.file

34. How to reset commit?

35. ❖ git reset C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”

36. ❖ git reset C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
a.file
“the C4 commit line”
-“the C5 commit line”
master
HEAD
“the C4 commit line”
“the C5 commit line”
a.file

37. What is soft reset?

38. ❖ git reset --soft C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”

39. ❖ git reset --soft C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
a.file
“the C4 commit line”
“the C5 commit line”
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”

40. What is hard reset?

41. ❖ git reset --hard C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
master
HEAD
a.file
“the C4 commit line”
“the C5 commit line”

42. ❖ git reset --hard C4
C1 C2 C3 C4 C5
Working
Directory
Stage
(index)
a.file
“the C4 commit line”
-“the C5 commit line”
master
HEAD
a.file
“the C4 commit line”
-“the C5 commit line”

43. QA