Understanding git

This is an internal training I made at Blablacar to better understand Git with visual graphics.

Transcript

2. Today’s topics
3. Today’s topics The basics of commit
 git add, commit, revert, reset How to move in a git tree
 git checkout, HEAD References
 git branch, tag, merge History manipulation
 git cherry-pick, git rebase (—interactive) Working with a remote server
 git clone, remote, push, pull, fetch, merge, rebase
4. Requirement Before using Git, make sure you correctly configured your user: git config --global user.name "Matthieu Moquet"
 git config --global user.email matthieu@moquet.net write in your global ~/.gitconfig Your real name
5. What is Git? Git is a distributed version control system. It works by creating local snapshots of all your files, like a big copy/paste, but better optimized.
6. src/ Foobar.php Baz.php README.md src/ Foobar.php Baz.php README.md Workspace
7. src/ Foobar.php Baz.php README.md abcdef234 Initial commit Workspace
8. src/ Foobar.php Baz.php README.md New.php src/ Foobar.php Baz.php README.md New.php abcdef234 Initial commit Workspace
9. src/ Foobar.php Baz.php README.md New.php deadbeef42 A new file abcdef234 Initial commit Workspace
10. src/ Foobar.php Baz.php README.md New.php src/ Foobar.php Baz.php README.md New.php abcdef234 Initial commit deadbeef42 A new file Workspace
11. src/ Foobar.php Baz.php README.md New.php fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file Workspace internally it only stores the deltas between commits
12. fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file a commit: • is a snapshot of the sources • is identified by its hash (sha1) • has one (or many) parents • is immutable git commit once a commit is done, you can NOT modify it!
13. How to commit?
14. How to commit? Workspace Staging area Commit git add file.txt
15. How to commit? Workspace Staging area Commit git add file.txt git commit
16. How to commit? Workspace Staging area Commit git add file.txt git commit
17. ➜ git init ➜ vim README.md ➜ git status ➜ git add README.md ➜ git commit ➜ git status Initialized empty Git repository in /path/to/myproject/.git/ Untracked files: (use "git add <file>..." to include in what will be committed) ! README.md Changes to be committed: (use "git reset HEAD <file>..." to unstage) ! new file: README.md [master (root-commit) 4b60dee] My commit ➜ git status On branch master nothing to commit, working directory clean
18. ➜ git commit -A -m "Your commit message" Shortcut git add ALL FILES inline commit message
19. Best practice ➜ git add -p diff --git a/README.md b/README.md index 540550a..2f10d41 100644 --- a/README.md +++ b/README.md @@ -1 +1 @@ -This is an old line +This is the new line Stage this hunk [y,n,q,a,d,/,e,?]? y diff --git a/src/Foobar.php b/src/Foobar.php index 540550a..2f10d41 100644 --- a/src/Foobar.php +++ b/src/Foobar.php @@ -1 +1 @@ -class Foobar -{ - const BAZ = 'world'; -} Stage this hunk [y,n,q,a,d,/,e,?]? git add patch
20. ➜ git commit Capitalized, short (50 chars or less) summary ! More detailed explanatory text, if necessary. Wrap it to about 72 characters or so. In some contexts, the first line is treated as the subject of an email and the rest of the text as the body. The blank line separating the summary from the body is critical (unless you omit the body entirely); tools like rebase can get confused if you run the two together. ! Write your commit message in the imperative: "Fix bug" and not "Fixed bug" or "Fixes bug." ! - Bullet points are okay, too - Use a hanging indent Best practice Open in your editor http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
21. Best practice commit 9342a5bf855042b29a2ebd3413ce8e6cfb65557f Author: Matthieu Moquet <matthieu@moquet.net> Date: Thu Sep 18 13:37:00 2014 +0200 ! Allow scope to be defined in the request entity body ! As defined in the RFC 6749: http://tools.ietf.org/html/rfc6749#section-4.4.2 ! Note that this change is backward compatible as it will first look up the request query.
22. Best practice commit c1230da7409d22fe78263da777da237e9fc702d4 Author: Matthieu Moquet <matthieu@moquet.net> Date: Tue Jul 29 17:00:33 2014 +0200 ! Use UserChecker in OAuth2 listener ! In order to deny block users on every API call ! Fix https://jira.example.net/browse/FOO-123
23. How to display the diff between commits?
24. git show abcdef Display the commit message + the diff with the previous one git diff abcdef dfebca Display the diff between the two commits git diff abcd~ abcd How to display the diff between commits?
25. git diff --staged Display the change put in the staging area git diff Display the file I changed but not committed/staged How to display the diff between commits?
26. Remember when I said a commit is immutable?
27. What if I made a mistake and want to rollback the committed code?
28. Case #1 I made a typo on my previous commit, let’s fix it quickly
29. git commit --amend Replace previous commit with new one, using the staging area git commit Oops, I made a mistake (typo, forget file, wrong commit msg) git add the_file.txt Add the concerned file into the staging area
30. Case #2 I want to remove the previous commit
31. git commit Meh, I shouldn’t have committed git reset HEAD~ Cancel the commit, but keep the change locally, so you can create another one git reset --hard HEAD~ Cancel the commit, and remove all the change
32. Case #3 I need to revert one or several commits already pushed into production
33. git commit Later: oops this commit (abc123) breaks something git revert abc123 Create a new commit, which is the opposite of the given one
34. demo
35. git log
36. git log master HEAD fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file Helps you to visualize the git tree start from a given commit… …and follow the parents to go through the history
37. commit 9342a5bf855042b29a2ebd3413ce8e6cfb65557f Author: Matthieu Moquet <matthieu@moquet.net> Date: Thu Sep 18 13:37:00 2014 +0200 ! Allow scope to be defined in the request entity body ! As defined in the RFC 6749: http://tools.ietf.org/html/rfc6749#section-4.4.2 ! Note that this change is backward compatible as it will first look up the request query. ! commit c851bca7bf85504fe82639342acb237e9fc87420 Author: Matthieu Moquet <matthieu@moquet.net> Date: Tue Jul 30 12:34:56 2014 +0200 ! Update README.md ! commit c1230da7409d22fe78263da777da237e9fc702d4 Author: Matthieu Moquet <matthieu@moquet.net> Date: Tue Jul 29 17:00:33 2014 +0200 ! Use UserChecker in OAuth2 listener ! In order to deny block users on every API call ! Fix https://jira.example.net/browse/FOO-123 git log
38. [alias] lg = log --graph --abbrev-commit --date=relative \ --pretty=tformat:'%Cred%h%Creset -... %s %Cgreen(%an %cr)%Creset' git log Shortcut
39. * 1187cf9 - (HEAD, master) Merge branch ‘update-ui' (Matthieu Moquet 2 hours ago) |\ | * 3b1ba4e - Compile assets via Gulp (Matthieu Moquet 2 hours ago) | * 90575d5 - Fix layout login dependency (Matthieu Moquet 2 hours ago) | * a151f92 - Update editor shortcuts (Matthieu Moquet 2 hours ago) |/ * 56fa6f3 - Merge branch 'project-page' (Matthieu Moquet 3 hours ago) |\ | * 2ee4b97 - Add inLocale parameter to project page (Matthieu Moquet 4 hours ago) | * 73b044f - Update navbar user menu UI (Matthieu Moquet 4 hours ago) | * 6faa5c3 - Rework project page (Matthieu Moquet 6 hours ago) |/ * 0309542 - Merge branch 'rework-model' (Matthieu Moquet 30 hours ago) |\ | * 0082ea5 - Fix duplicate key error on import processor (Matthieu Moquet 2 days ago) | * 8dab5be - Add options parameters for export api (Matthieu Moquet 2 days ago) | * 0649be9 - Warmup symfony cache in Travis build (Matthieu Moquet 2 days ago) | * 6c72e8e - Refactor app architecture (Matthieu Moquet 2 days ago) |/ * 77cb4c9 - Remove old scripts (Matthieu Moquet 4 days ago) * ... * * git lg
40. git checkout HEAD
41. git checkout master fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file Workspace ➜ git checkout abcdef234 HEAD
42. git checkout master HEAD fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file Workspace copy files
43. src/ Foobar.php Baz.php README.md New.php fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file Workspace HEAD
44. src/ Foobar.php Baz.php README.md New.php fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file Workspace HEAD
45. Workspace src/ Foobar.php Baz.php README.md fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file HEAD
46. git checkout abcd1234 -- file.txt Copy the file.txt from abcd1234 to local workspace
47. git checkout HEAD -- file.txt Cancel the changes of file.txt git checkout file.txt
48. Branches
49. Branches master HEAD fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file A branch is just a pointer to a commit foobar ➜ git branch foobar deadb33f42
50. Branches Internally a branch is simply a reference in a file ➜ cat .git/refs/heads/foobar deadb33f42d89b21f72f8115e34ad23c507db8b6 ➜ cat .git/HEAD ref: refs/heads/foobar So does HEAD ➜ cat .git/HEAD deadb33f42d89b21f72f8115e34ad23c507db8b6 git checkout foobar git checkout deadb33f42
51. Branches When committing, the reference pointed by the HEAD is moved to the new commit master HEAD abcdef234 Initial commit deadb33f42 A new file
52. Branches When committing, the reference pointed by the HEAD is moved to the new commit master HEAD fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file
53. Branches If HEAD points to a commit (and not a branch), then no branch will be updated master abcdef234 Initial commit deadb33f42 A new file HEAD
54. Branches master HEAD fear8342abc Update foobar abcdef234 Initial commit deadb33f42 A new file If HEAD points to a commit (and not a branch), then no branch will be updated orphan commit, no branch is referencing it
55. Shortcut Create a new branch and checkout it immediately. ➜ git branch foobar ; git checkout foobar ➜ git checkout -b foobar
56. demo
57. Merges Branches are useful when you’re working on a new feature. Once the feature is done you want it to be merged into the master branch.
58. foobar HEAD master ➜ git merge foobar Divergence —> create new commit
59. foobar HEAD master ➜ git merge foobar Divergence —> create new commit
60. foobar HEAD master ➜ git merge foobar No divergence —> Fast Forward
61. foobar HEAD master ➜ git merge foobar No divergence —> Fast Forward
62. foobar HEAD master ➜ git merge foobar --no-ff Force no Fast Forward
63. foobar HEAD master ➜ git merge foobar --no-ff Force no Fast Forward
64. History manipulation
65. Merge Hell
66. More readable
67. Better (no fast-forward)
68. HEAD master Understanding cherry-pick foobar Cherry-pick make a copy of a given commit
69. HEAD master Understanding cherry-pick ➜ git cherry-pick foobar~ foobar
70. HEAD master foobar Understanding cherry-pick ➜ git cherry-pick foobar
71. HEAD master foobar Understanding cherry-pick ➜ git branch -D foobar
72. HEAD master Understanding cherry-pick
73. Let’s automatize with Rebase
74. HEAD master Let’s automatize with Rebase ➜ git rebase master foobar
75. HEAD master Let’s automatize with Rebase foobar ➜ git rebase master
76. master Let’s automatize with Rebase foobar HEAD ➜ git rebase master
77. master Let’s automatize with Rebase foobar HEAD ➜ git rebase master
78. HEAD master Let’s automatize with Rebase foobar ➜ git merge --no-ff foobar master
79. HEAD master Let’s automatize with Rebase foobar ➜ git merge --no-ff foobar master
80. Interactive Rebase
81. HEAD master Interactive Rebase ➜ git rebase -i master foobar pick 1df2b98 My green commit pick 3b7aff0 My yellow commit pick 2edf2b8 My purple commit
82. HEAD master Interactive Rebase ➜ git rebase -i master foobar pick 1df2b98 My green commit pick 3b7aff0 My yellow commit pick 2edf2b8 My purple commit
83. HEAD master Interactive Rebase ➜ git rebase -i master foobar
84. master Interactive Rebase ➜ git rebase -i master foobar HEAD
85. master Interactive Rebase ➜ git rebase -i master foobar HEAD
86. master Interactive Rebase ➜ git rebase -i master foobar HEAD
87. HEAD master Interactive Rebase ➜ git rebase -i master foobar pick 1df2b98 My green commit pick 2edf2b8 My purple commit pick 3b7aff0 My yellow commit
88. HEAD master Interactive Rebase ➜ git rebase -i master foobar pick 1df2b98 My green commit squash 2edf2b8 My purple commit pick 3b7aff0 My yellow commit
89. HEAD master Interactive Rebase ➜ git rebase -i master foobar
90. master Interactive Rebase ➜ git rebase -i master foobar HEAD
91. master Interactive Rebase ➜ git rebase -i master foobar HEAD
92. master Interactive Rebase ➜ git rebase -i master foobar HEAD
93. master Interactive Rebase ➜ git rebase -i master foobar HEAD
94. Interactive Rebase # Commands: # p, pick = use commit # r, reword = use commit, but edit the commit message # e, edit = use commit, but stop for amending # s, squash = use commit, but meld into previous commit # f, fixup = like "squash", but discard this commit's log message # x, exec = run command (the rest of the line) using shell
95. demo
96. Working with a remote server
97. origin/master origin/foobar Working with a remote server git clone git@server.com master foobar
98. Working with a remote server origin/master master origin/foobar master foobar
99. Updating your local copy of remote branches origin/master master origin/foobar master foobar git fetch When the branch is updated on the server, you have to synchronize you local copy
100. Updating your local copy of remote branches origin/master master origin/foobar master foobar git fetch fetch will only update the origin/* branches
101. Updating your local branch fast-forward master master origin/master
102. master master origin/master git fetch Updating your local branch fast-forward
103. master master origin/master git fetch Updating your local branch fast-forward
104. master master origin/master git merge origin/master master Updating your local branch fast-forward
105. master master origin/master Updating your local branch fast-forward
106. Shortcut: git pull git pull origin master == git fetch origin ; git merge origin/master
107. Protip Never use git pull, except for master branch* *because you’re not supposed to have divergence with master
108. master origin/master Updating your local branch with divergence master
109. origin/master Updating your local branch with divergence master master someone have added commits into master
110. master origin/master Updating your local branch with divergence master me too git fetch
111. origin/master Updating your local branch with divergence master master git merge origin/master master
112. origin/master Updating your local branch with divergence master master Way to Merge-Hell (even with a single branch)
113. origin/master Updating your local branch with divergence master master git rebase origin/master
114. origin/master Updating your local branch with divergence master master
115. origin/master Updating your local branch with divergence master master git push origin master
116. origin/master Updating your local branch with divergence master master
117. Never use git pull. Instead do git fetch + git rebase or git pull --rebase
118. Basic Git Workflow
119. Master Initially we only have one master branch Basic Git Workflow
120. Master Branch We create a new branch to start a new feature Basic Git Workflow
121. Master Branch Once the feature done, we merge it into master Basic Git Workflow
122. Master Then we can safely delete the branch Basic Git Workflow
123. master master origin/master Basic Git Workflow ➜ git chekcout -b dev ➜ git commit; git commit
124. master master dev origin/master Basic Git Workflow ➜ git push origin dev
125. master master dev origin/master Basic Git Workflow dev origin/dev Meanwhile, master have been updated…
126. master master dev origin/master Basic Git Workflow dev origin/dev ➜ git fetch
127. master master origin/master Basic Git Workflow dev origin/dev dev ➜ git rebase origin/master
128. master master origin/master Basic Git Workflow dev origin/dev dev
129. master master origin/master Basic Git Workflow dev origin/dev dev git push origin dev Server will reject the push because of the divergence
130. master master origin/master Basic Git Workflow dev origin/dev dev git push -f origin dev Say the server to forget its old commits Use with caution if several people work on that branch
131. master master origin/master Basic Git Workflow origin/dev dev git push -f origin dev dev
132. master master origin/master Basic Git Workflow origin/dev dev dev ➜ git merge --no-ff dev master
133. master master origin/master Basic Git Workflow origin/dev dev Merged with Stash (non fast-forward)
134. master master origin/master Basic Git Workflow origin/dev dev Prune option delete removed origin/* branches ➜ git fetch -p
135. master master origin/master Basic Git Workflow dev ➜ git checkout master ! ➜ git merge origin/master or ➜ git pull
136. master origin/master Basic Git Workflow dev master ➜ git branch -d dev
137. master origin/master Basic Git Workflow master
138. TL;DR
139. ➜ git:(master) git pull # ensure your master is up to date Updating 7afe47a..fb562e8 Fast-forward ➜ git:(master) git checkout -b feat-something-1234 # start new branch ➜ git:(feat-something-1234) vim files ; git add -p ; git commit # commit code Switched to a new branch 'feat-something-1234' ➜ git:(feat-something-1234) git push -u origin feat-something-1234 To ssh://git@server/path/to/project.git + fb562e8...4b60dee feat-something-1234 -> feat-something-1234 [feat-something-1234 4b60dee] Some commit message ➜ git:(feat-something-1234) git rebase origin/master # update your branch First, rewinding head to replay your work on top of it... Applying: Some commit message ➜ git:(feat-something-1234) git fetch -p # later, before merging ➜ git:(feat-something-1234) git push -f # push force To ssh://git@server/path/to/project.git + fb562e8...4b60dee feat-something-1234 -> feat-something-1234 (force update) ➜ git:(feat-something-1234) stash pull-request master # open a PR ➜ git:(feat-something-1234) meps deploy # deploy on maquette
140. Bonus
141. Push git push origin foobar:foobar Long command git push origin :foobar Deleting a remote branch branch name on the remote local branch name into the remote branch push nothing
142. Push git push -u origin foobar Track upstream branch (the first time you push it) git push Use the shortcut the next time [push] # git < v2.0 # 'nothing' : Do not push anything # 'matching' : Push all matching branches (default) # 'upstream' : Push the current branch to whatever it is tracking # 'current' : Push the current branch default = upstream
143. Push git push origin foobar:foobar Push into the branch with the same branch by default git push [push] # git >= v2.0 default = simple
144. Track untracked file git add -N . Useful because git add patch only works on tracked file git add -p
145. Rebase conflict HEAD master foobar Problem: sometimes it happens you have to resolves several times the same conflict while rebasing Solution: squash all your commits before rebasing on master
146. Rebase conflict HEAD master foobar conflicts (1) git rebase origin/master origin/master
147. Rebase conflict HEAD master foobar conflicts (2) origin/master
148. Rebase conflict HEAD master foobar conflicts (3) origin/master
149. Rebase conflict HEAD master foobar git rebase -i $(git merge-base master foobar) origin/master First rebase on yourself There won’t be any conflict here
150. Rebase conflict HEAD master foobar origin/master pick 1df2b98 My green commit squash 3b7aff0 My yellow commit squash 2edf2b8 My purple commit
151. Rebase conflict HEAD master origin/master
152. Rebase conflict master origin/master HEAD
153. Rebase conflict master origin/master HEAD
154. Rebase conflict master origin/master HEAD
155. Rebase conflict master origin/master HEAD
156. Rebase conflict master origin/master HEAD foobar
157. Rebase conflict master origin/master HEAD foobar git rebase origin/master Then you can rebase on master
158. Rebase conflict master origin/master HEAD foobar git rebase origin/master Resolve conflicts once
159. Rebase conflict $ (vim the file.txt with the conflict) $ git add file.txt $ git rebase --continue To resolve a rebase conflict $ git rebase --abort If you fucked up
160. Branch diff $ git diff origin/master...foobar Diff for a whole branch $ git diff --name-status origin/master... Only display changed files $ git lg origin/master..foobar Log of the branch
161. Branch naming feat-description-1234 feat-description-BBCTHREE-1234 fix-description-1234 Internal convention to name a branch
162. Git Stash git stash save "WIP something" Want to save your change, but don’t want to commit? git stash pop git stash list Try not to have too many thing in your stash, otherwise you will forgot it git stash show -p stash@{0}
163. (last) demo
164. http://git-scm.com/ https://try.github.io/ http://pcottle.github.io/learnGitBranching/ http://www.git-attitude.fr/2014/05/04/bien-utiliser-git-merge-et-rebase/ http://www.git-attitude.fr/2014/09/15/30-options-git-qui-gagnent-a-etre-connues/ Links