Git internals + Git flow

Review of the main Git commands and how to mix them together to effectively work with people

Transcript

1. Git internals + Git flow Sergio Gutiérrez Mota Senior mobile engineer at Karumi
2. Pedro Vicente Gómez Alberto Gragera Jorge Barroso Davide Mendolia Senior Mobile Developer Technical Director Senior Android Developer Senior Full Stack Engineer
3. WHAT IS GIT? Version Control System + filesystem commit merge fetch add rebase
4. snapshots over changesets distributed over centralised branching over linear history WHAT IS GIT?
5. > git init • Creates a new repository • # just a .git folder describing your new filesystem • Only in your computer • Not tracking anything (yet) LET THERE BE GIT
6. .git !"" HEAD !"" objects #"" refs !"" heads #"" tags > git init LET THERE BE GIT
7. > git add • Saves file contents in a blob object • # SHA-1 + contents • Tracks the file including it in the index • # A file saving other files metadata SNAPSHOTTING
8. .git !"" HEAD !"" index !"" objects $ #"" a1 $ #"" 9abfea0f… #"" refs !"" heads #"" tags > git add • index contains a list of files metadata: • permissions • SHA-1 • name • the name of blob files are SHA-1s • Their content is a binary with the contents of the file they are storing SNAPSHOTTING
9. > git add > git ls-files --stage 100644 a19abfea0… 0 file.txt > git show a19abfea0 Hola GIT SNAPSHOTTING
10. > git commit • Takes every file listed in the index and builds a tree object • Creates a commit object and points it to the tree object SNAPSHOTTING
11. > git commit .git !"" HEAD !"" index !"" objects $ !"" 18 $ $ #"" 611beb72… $ !"" 87 $ $ #"" 1e25a902… $ #"" a1 $ #"" 9abfea0f #"" refs !"" heads #"" tags • trees are regular git objects containing file references and metadata • commits are also objects holding: • tree reference • author • committer • parent • message SNAPSHOTTING
12. > git commit > git ls-tree 18611beb72 100644 blob a19abfea0… file.txt > git show -s --pretty=raw 871e25a902 commit 871e25a902ed4309e94c2f39aa7102557a380f49 tree 18611beb7265e1af0b87190179be4d78ef80862a author Sergio Gutierrez <sergio@gokarumi.com> 1458666886 +0100 committer Sergio Gutierrez <sergio@gokarumi.com> 1458666886 +0100 First commit SNAPSHOTTING
13. > git commit a19abfea0f blob Hola GIT 18611beb72 tree blob a19abfea0f file.txt 871e25a902 commit tree 18611beb72 author Sergio committer Sergio parent - SNAPSHOTTING
14. > git commit a19abfea0f blob Hola GIT 18611beb72 tree blob a19abfea0f file.txt 871e25a902 commit tree 18611beb72 author Sergio committer Sergio parent - 2c492ae0a4 blob Adios GIT 779c601774 tree blob a19abfea0f file.txt blob 2c492ae0a4 other_file.txt c96b22adb6 commit tree 779c601774 author Sergio committer Sergio parent 871e25a902 SNAPSHOTTING
15. > git commit a19abfea0f blob Hola GIT 18611beb72 tree blob a19abfea0f file.txt 871e25a902 commit tree 18611beb72 author Sergio committer Sergio parent - 2c492ae0a4 blob Adios GIT 779c601774 tree blob a19abfea0f file.txt blob 2c492ae0a4 other_file.txt c96b22adb6 commit tree 779c601774 author Sergio committer Sergio parent 871e25a902 SNAPSHOTTING f0eaf19baa blob Hola GIT v2 779c601774 tree blob f0eaf19baa file.txt blob 2c492ae0a4 other_file.txt 7fbc204b8f
16. > git commit 871e25a902 commit tree 18611beb72 author Sergio committer Sergio parent - c96b22adb6 commit tree 779c601774 author Sergio committer Sergio parent 871e25a902 7fbc204b8f commit tree 22d693324f author Sergio committer Sergio parent c96b22adb6 snapshot 1 snapshot 2 snapshot 3 SNAPSHOTTING
17. > index a.k.a. stage a.k.a. cache • Stores what is going to be snapshotted for the next commit • One of the three trees git modify with every command SNAPSHOTTING
18. > index a.k.a. stage a.k.a. cache SNAPSHOTTING index working directory *commit git add git commit
19. > git status • Shows which files are different • Working directory - Index (ì) • Index - Current commit (ì) SNAPSHOTTING
20. > git diff • Shows all the changes in detail • Working directory - Index (default) • Index - Current commit (--staged) SNAPSHOTTING
21. > git branch • Creates a branch pointing to the current commit • By default, Git creates a branch called master BRANCHING
22. > git branch BRANCHING .git !"" HEAD !"" index !"" objects $ #"" … !"" refs $ !"" heads $ $ !"" master $ $ #"" my-branch $ #"" tags • A branch is just a text file with a reference to a commit • Branches are automatically updated when creating a new commit
23. > git branch BRANCHING > cat .git/refs/heads/master 7fbc204b8f3c0f85d7e86f5982d2bffe27ea742b > cat .git/refs/heads/my-branch 7fbc204b8f3c0f85d7e86f5982d2bffe27ea742b
24. > git branch BRANCHING master 7fbc204b8f c96b22adb6 871e25a902
25. > git branch BRANCHING master my-branch 7fbc204b8f c96b22adb6 871e25a902
26. > git branch + git commit BRANCHING master my-branch 7fbc204b8f c96b22adb6 e25a902
27. > git branch + git commit BRANCHING master my-branch 7fbc204b8f c96b22adb6 e25a902 0612faad12
28. > git checkout • Changes the working branch • The working branch is identified by a pointer called HEAD BRANCHING
29. > git checkout BRANCHING > cat .git/HEAD ref: refs/heads/master
30. > git checkout BRANCHING master my-branch 7fbc204b8f c96b22adb6 e25a902 HEAD 0612faad12
31. > git checkout BRANCHING master my-branch 7fbc204b8f c96b22adb6 e25a902 HEAD 0612faad12
32. > git checkout + git commit BRANCHING master my-branch 7fbc204b8f c96b22adb6 e25a902 HEAD 0612faad12
33. > git checkout + git commit BRANCHING master my-branch 7fbc204b8f c96b22adb6 e25a902 HEAD 0612faad12 24dd971a23
34. > git tag • Very similar to branches but are not updated automatically • There are two types: • lightweight • annotated BRANCHING
35. > git tag (lightweight) DIVERGING .git !"" HEAD !"" index !"" objects $ !"" … !"" refs $ !"" heads $ !"" !"" … $ #"" tags $ #"" my-lightweight-tag • A lightweight tag is a file text with a reference to a commit
36. > git tag (annotated) DIVERGING .git !"" HEAD !"" index !"" objects $ !"" … $ !"" 3e $ #"" 38efa5ea1f !"" refs $ !"" heads $ !"" !"" … $ #"" tags $ !"" my-annotated-tag $ #"" my-lightweight-tag • An annotated tag creates a tag object (very similar to a commit object) and points to it
37. > git reset • Reverts the state of the code to a previous version • There are 3 versions, depending on the scope of the revert: • soft • mixed • hard REVERTING
38. > git reset • Think of git reset as a three step process: 1. Move the current branch to REF 2. Revert index files to look like REF 3. Revert working directory files to look like REF REVERTING
39. > git reset -- soft (step 1) REVERTING my-branch 7fbc204b8f HEAD 919fbbc1d2 index index_file.txt index_other_file.txt working directory new_work.txt new_work_other_file.txt index_file.txt index_other_file.txt
40. > git reset -- soft (step 1) REVERTING my-branch 7fbc204b8f HEAD 919fbbc1d2 index index_file.txt index_other_file.txt working directory new_work.txt new_work_other_file.txt index_file.txt index_other_file.txt
41. > git reset -- mixed (step 2) REVERTING my-branch 7fbc204b8f HEAD 919fbbc1d2 index index_file.txt index_other_file.txt working directory new_work.txt new_work_other_file.txt index_file.txt index_other_file.txt
42. > git reset -- mixed (step 2) REVERTING my-branch 7fbc204b8f HEAD 919fbbc1d2 index file_in_919fbbc1d2.txt working directory new_work.txt new_work_other_file.txt index_file.txt index_other_file.txt
43. > git reset -- hard (step 3) REVERTING my-branch 7fbc204b8f HEAD 919fbbc1d2 index index_file.txt index_other_file.txt working directory new_work.txt new_work_other_file.txt index_file.txt index_other_file.txt
44. > git reset -- hard (step 3) REVERTING my-branch 7fbc204b8f HEAD 919fbbc1d2 index file_in_919fbbc1d2.txt working directory file_in_919fbbc1d2.txt
45. > git merge • If one of the branches is a subhistory of the other: • apply fast-forward • else: • creates a new commit with two parents COMBINING
46. > git merge (fast-forward) COMBINING master my-branch commit C commit B commit A
47. > git merge (fast-forward) COMBINING master my-branch commit C commit B commit A
48. > git merge COMBINING master my-branch commit A commit C commit B
49. > git merge COMBINING master my-branch commit A commit C commit B commit M
50. > git rebase • Finds the most recent common ancestor • Replays all the commits from one branch in the tip of the other • The operation rewrites history COMBINING v2
51. > git rebase COMBINING v2 master my-branch commit A commit C commit B
52. > git rebase COMBINING v2 master my-branch commit A commit C commit B commit C’
53. > git rebase • Interactive rebase let’s you rewrite history as you want • pick • reword • squash • … COMBINING v2
54. > git remote add • Adds yet another reference to find other copies of the repository • When using git clone, it will automatically add a default remote called origin SHARING
55. > git remote add SHARING .git !"" HEAD !"" index !"" config !"" objects $ !"" … !"" refs $ !"" heads $ !"" !"" … $ !"" remotes $ #"" tags [remote "origin"] url = git@github.com:Karumi/MyRepo.git fetch = +refs/heads/*:refs/remotes/origin/*
56. > git fetch • Brings everything contained in a remote to your local copy, including: • branches • commits • trees • blobs • … SHARING
57. > git fetch SHARING .git !"" HEAD !"" index !"" config !"" objects $ !"" … !"" refs $ !"" heads $ !"" !"" … $ !"" remotes $ $ !"" origin $ $ $ !"" master $ $ $ #"" my-branch $ #"" tags • A remote is nothing but a directory with a file for each branch • Remote branches are text files with the SHA-1 of the commit they are pointing to
58. > git fetch SHARING > cat .git/refs/remotes/origin/master 7fbc204b8f3c0f85d7e86f5982d2bffe27ea742b > cat .git/refs/remotes/origin/my-branch 7fbc204b8f3c0f85d7e86f5982d2bffe27ea742b
59. > git fetch SHARING master commit A commit B
60. > git fetch SHARING master origin/master commit A commit C commit B
61. > git pull • git fetch + git merge SHARING > git branch -u • Links a local branch with a remote branch • It will automatically pull and push to that remote branch without further specification
62. > git pull SHARING master commit A commit B
63. > git pull SHARING master origin/master commit A commit C commit B
64. > git pull SHARING master origin/master commit A commit C commit B commit M
65. SHARING > git push • Sends all local objects that are not in the remote • Syncs the branch or branches using fast- forward
66. EXTRA > git revert • Creates a reverse patch from the specified commit and applies on HEAD • Use it when you mistakenly pushed something on a branch shared with others
67. > git revert EXTRA master commit A commit B
68. > git revert EXTRA master commit A commit B commit ~B
69. EXTRA > git cherry-pick • Replays the specified commits on HEAD • Use it when you want to pick a single commit (a fix) and have it in your branch • Use it if you messed up real bad your history and want to recreate a branch
70. > git cherry-pick EXTRA master commit A commit B commit C my-branch commit Z
71. > git cherry-pick EXTRA master commit A commit B commit C my-branch commit Z commit C’
72. EXTRA > git stash • Saves your index and working directory • You can apply those changes anytime you want • There are multiple options available: • create • apply • list • pop
73. WORKING WITH A TEAM • Several ways of working together: • Centralised workflow • Feature branch workflow • Gitflow workflow • Forking workflow • Whatsoever workflow
74. WORKING WITH A TEAM • Several ways of working together: • Centralised workflow • Feature branch workflow • Gitflow workflow • Forking workflow • Whatsoever workflow
75. WORKING WITH A TEAM • Several ways of working together: • Centralised workflow • Feature branch workflow • Gitflow workflow • Forking workflow • Whatsoever workflow
76. WORKING WITH A TEAM • master • A history of all the releases • develop • Contains everything is going to be released • feature • New stuff always comes in brand new branches
77. WORKING WITH A TEAM master develop feature M1 D1 F1 F2 D3 M2 v1.0 v1.1 D2
78. WORKING WITH A TEAM develop D1
79. WORKING WITH A TEAM develop my-feature D1 F1
80. WORKING WITH A TEAM develop my-feature D1 F1 F2 D2
81. WORKING WITH A TEAM develop my-feature D1 F1 F2 D3 D2
82. WORKING WITH A TEAM master M1 v1.0 develop D1
83. WORKING WITH A TEAM master M1 v1.0 develop D1 D3 D2
84. WORKING WITH A TEAM master M1 M2 v1.0 develop D1 D3 D2
85. WORKING WITH A TEAM master M1 M2 v1.0 v1.1 develop D1 D3 D2
86. WORKING WITH A TEAM • release • Prepare all the release wise operations • bugfix • Same as a regular feature (might be merged to release branches) • hotfix • Branched from master, merges in master and develop
87. WORKING WITH A TEAM master develop M1 D1 v1.0
88. WORKING WITH A TEAM master release develop M1 R1 D1 v1.0
89. WORKING WITH A TEAM master release develop M1 R1 D1 D2 v1.0 R2
90. WORKING WITH A TEAM master release develop M1 R1 D1 D2 M2 v1.0 R2
91. WORKING WITH A TEAM master release develop M1 R1 D1 D2 M2 v1.0 R2 D3
92. WORKING WITH A TEAM master release develop M1 R1 D1 D2 M2 v1.0 v1.1 R2 D3
93. WORKING WITH A TEAM master develop M1 D1 D2 v1.0
94. WORKING WITH A TEAM master hotfix develop M1 H1 D1 D2 v1.0
95. WORKING WITH A TEAM master hotfix develop M1 H1 D1 D2 v1.0 H2
96. WORKING WITH A TEAM master hotfix develop M1 H1 D1 D2 M2 v1.0 H2
97. WORKING WITH A TEAM master hotfix develop M1 H1 D1 D2 M2 v1.0 H2 D3
98. WORKING WITH A TEAM master hotfix develop M1 H1 D1 D2 M2 v1.0 v1.1 H2 D3
99. FAQ > How do I solve merge conflicts? • You will see the code of your current branch (HEAD) vs the code of the branch you are bringing • Use your favourite text editor or your favourite tool
100. FAQ > How do I solve merge conflicts? <<<<<<< HEAD public void myOtherMethod() { ======= public bool myMethod() { >>>>>>> master My code vs Others code
101. FAQ > How do I solve merge conflicts? public bool myOtherMethod() { Our code
102. FAQ > How do I solve merge conflicts? • While rebasing, my code is the branch you are rebasing to!
103. FAQ > How do I see the differences between two branches? • git diff branch1..branch2
104. FAQ > How do I revert a non-pushed commit? • git reset --hard HEAD^
105. > git reset --hard HEAD^ FAQ my_branch commit A commit B origin/my_branch
106. > git reset --hard HEAD^ FAQ my_branch commit A commit B origin/my_branch
107. FAQ > How do I revert a non-pushed commit but keeping its contents? • If you only want to add files and/or change the commit message: • git commit --amend • else: • git reset --soft HEAD^
108. > git commit --amend FAQ my_branch commit A commit B origin/my_branch
109. > git commit --amend FAQ my_branch commit A commit B origin/my_branch commit B’
110. FAQ > How do I revert a pushed commit? • If you can rewrite history: • git reset --hard HEAD^ • git push -f • else: • git revert HEAD
111. > git revert HEAD FAQ my_branch commit A origin/my_branch
112. > git revert HEAD FAQ my_branch commit A commit ~A origin/my_branch
113. FAQ > How do I change my current branch keeping my work? • Use one of the tools you learned so far: • git commit • git stash
114. FAQ > How do I revert a merge? • If you can rewrite history: • git reset --hard HEAD^ • git push -f • else: • git revert HEAD -m1
115. > git reset --hard HEAD^ FAQ master my-branch commit A commit C commit B commit M
116. > git reset --hard HEAD^ FAQ master my-branch commit A commit C commit B commit M
117. > git revert -m1 HEAD FAQ master my-branch commit A commit C commit B commit M
118. > git revert -m1 HEAD FAQ master my-branch commit A commit C commit B commit M commit ~M
119. > git revert -m1 HEAD (caveats) FAQ master commit M commit ~M my-branch commit C commit B
120. > git revert -m1 HEAD (caveats) FAQ master commit M commit ~M my-branch commit C > git merge my-branch Already up-to-date. commit B
121. > git revert -m1 HEAD (caveats) FAQ master commit M commit ~M
122. > git revert -m1 HEAD (caveats) FAQ master commit M commit ~M commit ~~M
123. > git revert -m1 HEAD (caveats) FAQ master commit M commit ~M commit ~~M my-branch commit C commit D
124. > git revert -m1 HEAD (caveats) FAQ master commit M commit ~M commit ~~M my-branch commit C commit D commit M2
125. FAQ Your questions?
126. I NEED MORE (BOOKS) • Pro Git #Book with an in-depth explanation about how Git works • Git community book #A collaborative online book about Git, complementary of the first
127. I NEED MORE (ONLINE) • try.github.io #Really basic tutorial with a console to interact with git • pcottle.github.io/learnGitBranching #A complete tutorial of Git branches, includes rebasing and an awesome visualization • git-it # Online workshop from your terminal
128. I NEED MORE (TOOLS) • SourceTree #Standard VCS desktop client • GitUp #Best visualization tool • GitHub Desktop #Simple client for GitHub • GitKraken #Desktop client focused on fancy visuals
129. Find me! @serchinastico sergio@karumi.com https:/ /github.com/serchinastico