This document provides guidance on writing clear and informative commit messages in Git. It recommends including a short summary as the first line, keeping the first line under 50 characters, starting with a capital letter, omitting periods, and using the imperative mood. For longer messages, it suggests including an empty line between the summary and description, focusing on what changed and why rather than how, and wrapping text at 72 characters. Examples of good Git repositories are also provided.

1. Keep your GIT history
clean
Tomasz Brodziński
@TomaszBro

3. meaningless messages
“fixing bug”, “minor changes”, “clean up”, “oops”

4. repeated messages
“fix bug 9876”
“fix bug 9876”
“fix bug 9876”

5. tickets numbers only
“BUG-1234”

6. duplicating the code
“add property `foo`”

7. too long messages
“It is the big and important commit, which introduces
new functionality to our great application.”

8. too big commits

9. Commit message – formating and limitations

10. First line as summary of changes
● max 50 characters

11. First line as summary of changes
● max 50 characters
● begin with a capital letter

12. First line as summary of changes
● max 50 characters
● begin with a capital letter
● no period at the end

13. First line as summary of changes
● max 50 characters
● begin with a capital letter
● no period at the end
● imperative mood

14. Detailed description
● empty line

15. Detailed description
● empty line
● “what”, “why” not “how”

16. Detailed description
● empty line
● “what”, “why” not “how”
● wrap at 72 characters

17. Detailed description
● empty line
● “what”, “why” not “how”
● wrap at 72 characters
● markup syntax

18. Examples of good git repositories
● Git (https://github.com/git/git/commits/master)
● Linux kernel (https://github.com/torvalds/linux/commits/master)
● Spring Boot
(https://github.com/spring-projects/spring-boot/commits/master)

20. > git commit --amend
Modifying last commit

22. Undo last commits
> git reset HEAD~1

23. Undo last commits
> git reset HEAD~1

24. Undo last commits
> git reset HEAD~1
> git reset --hard HEAD~1

26. Undo commit
> git revert <commit>

27. Undo commit
> git revert <commit>

28. Three-way merge
C1 C5C2
C3 C4
C6
feature
master

29. Three-way merge
C1 C5C2
C3 C4
C6
feature
C7
master

30. Rebasing
C1 C5C2
master
C3 C4
C6
feature

31. Rebasing
C1 C5C2
master
C6
> git rebase master
C3' C4'
feature
C3 C4
feature

32. Rebasing
C1 C5C2
master
C6
> git rebase master
C3' C4'
feature
C3 C4
feature

33. Interactive rebasing
> git rebase -i HEAD~5

35. Interactive rebasing
modifying commit message
pick a2936e8 commit 1
reword 8f6e450 commit 2
pick dabb0ef commit 3
pick ef5a182 commit 4
pick 4df80af commit 5

36. Interactive rebasing
editing commit
pick a2936e8 commit 1
pick 4ef5850 new message
edit dabb0ef commit 3
pick ef5a182 commit 4
pick 4df80af commit 5

37. Rebasing
> git rebase --skip
> git rebase --continue
> git rebase --abort

38. Interactive rebasing
removing commit
pick a2936e8 commit 1
pick 4ef5850 new message
pick dabb0ef commit 3
pick ef5a182 commit 4
pick 4df80af commit 5

39. Interactive rebasing
removing commit
pick a2936e8 commit 1
pick 4ef5850 new message
pick dabb0ef commit 3
pick 4df80af commit 5

40. Interactive rebasing
squash commits
pick a2936e8 commit 1
pick 4ef5850 new message
squash a733bfe edited commit
pick 4df80af commit 5

41. Interactive rebasing
fixup commit
pick a2936e8 commit 1
pick e95fadc squashed commit
pick 4df80af commit 5
fixup 865ef03 commit 6
pick 4ee98c2 commit 7

42. Interactive rebasing
fixup commit
pick a2936e8 commit 1
fixup 865ef03 commit 6
pick e95fadc squashed commit
pick 4df80af commit 5
pick 4ee98c2 commit 7

43. Interactive rebasing
running shell command
pick 37ef6a3 commit 1
pick e95fadc squashed commit
exec make test
pick 4df80af commit 5
exec cd subdir; make test
pick 4ee98c2 commit 7

44. Fixup commit
> git commit --fixup=4df80af

45. Fixup commit
> git rebase -i --autosquash HEAD~5
pick a2936e8 commit 1
pick e95fadc squashed commit
pick 4df80af commit 5
fixup 723de73 fixup! commit 5
pick 4ee98c2 commit 7

46. Squash commit
> git commit --squash=a2936e8

47. Squash commit
> git rebase -i --autosquash HEAD~5
pick a2936e8 commit 1
squash 723de73 squash! commit 1
pick e95fadc squashed commit
pick 4df80af commit 5
pick 4ee98c2 commit 7

49. Reflog
> git reflog
8a8fa91 HEAD@{0}: merge branch1: Merge made by the
'recursive' strategy.
ddae7c1 HEAD@{1}: checkout: moving from branch1 to master
50465c0 HEAD@{2}: commit: Commit 4
ddae7c1 HEAD@{3}: commit: Commit 3
f15e834 HEAD@{4}: commit: My commit 2
4df80af HEAD@{5}: checkout: moving from master to branch1
4df80af HEAD@{6}: commit (initial): My first commit

50. Reflog
> git reset --hard HEAD@{3}

51. IDE vs terminal

52. Git log - filtering
> git log <origin>..<branch>

53. Git log - filtering
> git log --grep <search>
> git log <origin>..<branch>

54. Git log - filtering
> git log --grep <search>
> git log --before <date>
> git log <origin>..<branch>

55. Git log - filtering
> git log --grep <search>
> git log --before <date>
> git log --after <date>
> git log <origin>..<branch>

56. Git log - filtering
> git log --grep <search>
> git log --before <date>
> git log --after <date>
> git log --author <author name>
> git log <origin>..<branch>

57. Git log - formating
> git log

58. Git log - formating
> git log
> git log --oneline

59. Git log - formating
> git log
> git log --oneline
> git log --graph

60. Git log - formating
> git log
> git log --oneline
> git log --graph
> git log --decorate

61. Git log - formating
> git log
> git log --oneline
> git log --graph
> git log --decorate
> git log --oneline --graph --decorate

63. Thank you!