Git Anti-Patterns: Extended Version With 28 Common Anti-Patterns

These are the slides containing 28 anti-patterns in Git. I present these slides at 2 hours meetups and seminars.

Transcript

1. GITANTI PATTERNS How To Mess Up With Git and Love It Again LEMi ORHAN ERGiN Agile Software Craftsman, iyzico /lemiorhan lemiorhanergin.com @lemiorhan 28 common git anti-patterns
2. DISCLOSURE There is no formula for using git efficiently. Opinions are my own. It means the opposites might work perfectly for your conditions.
3. git is powerful but you have to know using it properly
4. Are you using git if all you do is commit-push-pull use dropbox instead ANTIPATTERN DANGER as if it is dropbox ? 1 DROPBOX-ISH GIT ANTI-PATTERN
5. learn how git works no worries, I will cover how git behaves
6. the way it keeps FILES & FOLDERS working copy staging area objects database repository the way it keeps REFERENCES directed acyclic graph keeping snapshots traversing graph branches, tags, heads git has 2 mechanisms
7. Source Code Working Copy you want to version changes
8. Source Code Working Copy $ git init Object Database .git Folder / Object Database Cache Staging Area / The Index initializing repo
9. Source Code Working Copy $ git init --bare Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server initializing bare repo
10. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git add . preparing commits
11. folder folder folder file file file $ git add . preparing commits
12. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git add . preparing commits
13. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git commit -m “initial commit” commi!ing
14. $ git commit -m “initial commit” commi!ing folder folder folder file file file commit branch HEAD For more details, refer to book Git Internals by Scott Chacon
15. folder folder folder file file file commit $ git commit -m “second commit” commi!ing folder commit branch HEAD folder file folder For more details, refer to book Git Internals by Scott Chacon
16. folder folder folder file file file commit $ git commit -m “third commit” commi!ing folder commit folder file folder folder commit branch HEAD file For more details, refer to book Git Internals by Scott Chacon
17. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git commit -m “initial commit” commi!ing
18. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git remote add origin http://upstream.repo $ git push -u origin master pushing to remote
19. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy new changes from others are pushed
20. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git fetch fetching changes
21. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git merge FETCHED_HEAD updating working copy
22. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git pull git fetch + git merge ge!ing changes to source code
23. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy want to update last commit
24. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git reset --soft $ git commit --amend / so" reseting cannot be reached Only the cache for the commit you reseted is removed from staging area for your current branch
25. folder folder folder file file file commit folder commit folder file folder folder commit branch HEAD file For more details, refer to book Git Internals by Scott Chacon $ git reset --soft $ git commit --amend / so" reseting
26. folder folder folder file file file commit folder commit folder file folder folder commit branch HEAD file For more details, refer to book Git Internals by Scott Chacon $ git reset --soft $ git commit --amend / so" reseting
27. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy want to squash or change last commits
28. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git reset --mixed mixed reseting cannot be reached entries for commits, files and folders are removed from staging area
29. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy want to get rid of last commits
30. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git reset --hard hard reseting cannot be reached removed from staging area removed from working copy
31. are you brave enough to jump to any commit ? jump to a branch create a branch from a commit create a branch from a tag ANTIPATTERN DANGER $ git checkout feature/PA-121 $ git checkout -b fix/missing-sign-parameter 2449be8 $ git checkout -b hotfix/v1.1 tags/v1 2 BROKEN TIME MACHINE ANTI-PATTERN
32. are you sure? are you brave enough to jump to any commit ?
33. do you have loooooong living topic branches ? ANTIPATTERN DANGER 3 LONG LIVING BRANCHES ANTI-PATTERN
34. do you have loooooong living topic branches ? welcome to merge hell
35. before merging do you validate commits back to source ? ANTIPATTERN DANGER code review, continuous integration, automated testing… 4 TOO LATE TO VALIDATE ANTI-PATTERN
36. before merging do you validate commits back to source ? are you sure?
37. merge and unmerge do you o!en want to just before releases ? ANTIPATTERN DANGER 5 CHERRY-PICK OBSSESSION ANTI-PATTERN
38. merge and unmerge do you o!en want to just before releases ? master HEAD TAG/v13 version 14 $ git cherry-pick Every-Single-Commit-We-Want-To-Deploy
39. the commit graph ? do you fully understand ANTIPATTERN DANGER 6 DEATH ON COMMIT GRAPH ANTI-PATTERN
40. the commit graph ? do you fully understand topic and shared branches, tracking branches, tags, HEADs, merge commits, reverted commits…
41. Cure?
42. Commit Early, Commit O"en Perfect Later, Publish Once
43. STEP 0 split your big feature into mini shippable tasks master HEAD TOPIC ORIGIN/master refactorings tasks, like rest endpoints testable, deployable each task will have a branch, not a feature
44. STEP 1 commit early commit o!en no need to compile no need for CI it’s only for versioning do not push master HEAD TOPIC ORIGIN/master
45. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master
46. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master
47. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master if you branch is pushed already $ git push -f
48. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master if you branch is pushed already $ git push -f Sync source branch a!erwards $ git fetch origin master:master
49. perfect later make it single commit $ git reset HEAD~3 or $ git rebase -i HEAD~3 HEAD TOPIC STEP 3 ORIGIN/master tests are passing app is working code is reviewed (*) master
50. $ git reset HEAD~3 (then commit) or $ git rebase -i HEAD~3 HEAD TOPIC STEP 3 ORIGIN/master perfect later make it single commit tests are passing app is working code is reviewed (*) master
51. Use feature flags/toggles HEAD TOPIC STEP 4 ORIGIN/master if feature should be disabled merge back to source $ git checkout master $ git merge topic master
52. Use feature flags/toggles master HEAD TOPIC STEP 4 ORIGIN/master if feature should be disabled merge back to source $ git checkout master $ git merge topic
53. Continuous Integration validates master branch continuously master HEAD TOPIC ORIGIN/master Pull requests can be used to review code and to validate before merging back to master Scrum tasks are mapped to commits, not stories Github Flow can be used to govern overall TAMING THE POWER OF GIT make git the king again Feature flags should be used whenever possible Commit early & o"en perfect later, publish once philosophy Deliver frequently be prepared to send every single commit Deleting branches a"er merge will make your commit graph readable
54. use terminal GUIs are prison balls of developers it’s ok to use GUIs while checking diffs, resolving conflicts and viewing commit graph BUTTON ADDICT ANTI-PATTERN 7 ANTIPATTERN DANGER
55. do not lose take extra care while using hard reset $ git reset --merge HEAD~ Use stash $ git stash save “updates local settings to keep db safe” $ git reset --hard HEAD~ $ git stash apply stash@{0} Create a new branch $ git checkout -b feature/PA-121 $ git add settings.xml $ git commit -m “adds new settings config” Use hard reset with merge and commit into it uncommited changes CODE LOSING SYNDROME ANTI-PATTERN 8 ANTIPATTERN DANGER
56. TOPIC HEAD MASTER $ git merge --squash fix Squash commit -- not updating HEAD Automatic merge went well; stopped before committing as requested $ git add . $ git commit -m “adds a feature” $ git branch -D topic TRASH HOUSE ANTI-PATTERN 9 long living branches with care handle ANTIPATTERN DANGER Squash all commits in your topic branch and 
 make them available in working copy
57. long living branches with care handle TOPIC HEAD MASTER $ git merge --squash fix Squash commit -- not updating HEAD Automatic merge went well; stopped before committing as requested $ git add . $ git commit -m “adds a feature” $ git branch -D topic Squash all commits in your topic branch and 
 make them available in working copy
58. stop adding prevent commits from being big ball of muds every change OMNIBUS BILL ANTI-PATTERN 10 ANTIPATTERN DANGER
59. stop adding prevent commits from being big ball of muds every change local change sets at JetBrains IDEs
60. stop adding every change partial add
61. messages are read! # WHAT # <issue id> (this commit will...) <subject> # WHY and HOW # Explain why this change is being made # RELATED # Provide links or keys to any relevant issues or other resources # REMEMBER # use lower case in the subject line # start with a verb in imperative tone in the subject line # do not end the subject line with a period # separate subject from body with a blank line # use the body to explain what and why vs. how # can use multiple lines with "-" for bullet points in body $ git config --global commit.template ~/.git-commit-template.txt $ git config --global commit.cleanup strip use git commit templates to create be"er commit messages com t m i F*CKING COMMIT MESSAGES ANTI-PATTERN 11 ANTIPATTERN DANGER
62. messages are read! use git commit templates to create be"er commit messages com t m i
63. by adding new commits ? do you rollback your mistakes ANTIPATTERN DANGER 12 MESS UP WITH THE ROLLBACK ANTI-PATTERN
64. hard reset the merge commit $ git reset --hard HEAD~ if you haven't pushed yet HEAD MASTER Bug fıx
65. never force push and change the history if you already pushed to shared branch Bug fıx HEAD MASTER
66. revert the merge commit $ git revert 8f937c6 -m 1 if you already pushed Bug fıx HEAD MASTER
67. is not the only method pushing commits to server ANTIPATTERN DANGER for sharing your code 13 CENTRALIZED GIT ANTI-PATTERN
68. Git Pong Pairing $ git remote add personA <URL> $ git fetch personA $ git checkout personA/master $ git checkout -b feature/PA-231 add your changes and commit $ git push personA feature/PA-231 A B $ git checkout feature/PA-231 add your changes and commit $ git pull personA feature/PA-231
69. with the ones in source branch ? how do you sync your commits ANTIPATTERN DANGER 14 MERGE FANATIC ANTI-PATTERN
70. Bug fıx ladder pa!ern occurs when premature merge happens HEAD MASTER
71. FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master
72. FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master
73. FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master
74. FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master c5 REPLAY #1
75. FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master c5 REPLAY #2 c6 c6
76. FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master c5 REWIND c6 c6
77. FIX master c1 c2 c3 c4 c7 HEAD use rebase $ git rebase master c5 FINALIZE c6 c6
78. deleting branches? are you scared of ANTIPATTERN DANGER 15 BRANCH CEMETERY ANTI-PATTERN
79. delete merged local branches $ git branch --merged | grep -v '^* master$' | grep -v '^ master$' | xargs git branch -d delete remote branches $ git branch -r --merged | grep -v master | sed 's/origin\///' | xargs -n 1 git push --delete origin
80. delete all merged local branches $ git branch --merged | grep -v '^* master$' | grep -v '^ master$' | xargs git branch -d delete all merged remote branches $ git branch -r --merged | grep -v master | sed 's/origin\///' | xargs -n 1 git push --delete origin
81. wri!en in any form? anyone can push any code ANTIPATTERN DANGER 16 UNCONTROLLED POWER ANTI-PATTERN
82. use pre-receive hooks
83. Depend on each other Too many repositories ANTIPATTERN DANGER for sharing your code 17 WEB OF REPOSITORIES ANTI-PATTERN
84. Mono Repository System Even though our services are still developed and deployed independently, the code for all services lives in one repository The repository contains more than one logical project (e.g. an iOS client and a web-application) These projects are most likely unrelated, loosely connected or can be connected by other means (e.g via dependency management tools) Twi#er, Facebook, Google, Digital Ocean, Foursquare, Etsy, Shippable, Plataformatec, Ravelin
85. You can not do CI without using monorepos - Xebia “When you start a new project,” Potvin tells WIRED, “you have a wealth of libraries already available to you. Almost everything has already been done.” - Rachel Potvin, Engineering Manager at Google Our productivity has increased at least 5x. - Shippable
86. v1, v2, v3… having branch for every release ANTIPATTERN DANGER 18 ORACLE SYNDROME ANTI-PATTERN at the same time
87. Commit early & o"en perfect later, publish once philosophy Deploy frequently be prepared to send every single commit Newer keep release branches for a long time master branch should be enough for all your needs
88. to git repo you pushed confidential info ANTIPATTERN DANGER 19 WAITING FOR HACKERS ANTI-PATTERN
89. Ref: https://help.github.com/articles/remove-sensitive-data/
90. Do you know what evil merge is? ANTIPATTERN DANGER 20 EVIL MERGE ANTI-PATTERN
92. do you use feature branches when there is no product at all ANTIPATTERN DANGER 21 BRANCH OVERDOSE ANTI-PATTERN
93. use single branch topic branches simply make everything more complex
94. Scared on using git commands ANTIPATTERN DANGER 22 CHUCKY THE COMMAND ANTI-PATTERN
95. push add dosya güncelleme committed Track ediliyor untracked unmodified pushed modified staged Staging Alanında Local Repoda Uzak Repoda added add commit commit
96. hard reset committed Track ediliyor untracked unmodified pushed modified staged Staging Alanında Local Repoda Uzak Repoda added hard reset hard reset mixed reset mixed reset soft reset rm --cached rm x
97. h"ps://github.com/lemiorhan/git-kata
98. no one knows git perfect do you suffer? ANTIPATTERN DANGER 23 NO HERO TO SAVE LIVES ANTI-PATTERN
99. have a git-man at least one developer should expertise on git for supporting the others
100. Having duplicate commits & Having irrelevant merge commits if you haven’t pushed yet ANTIPATTERN DANGER 24 DUPLICATE COMMITS ANTI-PATTERN
102. UPSTREAM LOCAL master c1 c2 c3 c4 c7 c5 c6 c5 c6 FIX HEAD master c1 c2 c3 c4 c7 c5 c6 c5 c6 FIX rebase and push
103. UPSTREAM LOCAL master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX HEAD master c1 c2 c3 c4 c7 c5 c6 c5 c6 FIX $ git rebase master rebase and push
104. UPSTREAM LOCAL master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX HEAD master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX $ git push -f rebase and push
105. UPSTREAM LOCAL master c1 c2 c3 c4 c7 c5 c6 c5 c6 FIX HEAD master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX pull rebased branch
106. UPSTREAM LOCAL master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX HEAD master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX $ git pull --rebase pull rebased branch
107. UPSTREAM LOCAL master c1 c2 c3 c4 c7 c5 c6 c5 c6 FIX HEAD master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX c5 c6 c5’ c6’ ORIGIN/FIX $ git pull pull rebased branch:(
108. UPSTREAM LOCAL c1 c2 c3 c4 c7 c5 c6 c5 c6 master c1 c2 c3 c4 c7 c5 c6 c5’ c6’ FIX c5 c6 c5’ c6’ c8 $ git pull master FIX HEAD ORIGIN/FIX pull rebased branch:(
109. we commit when we have something big ANTIPATTERN DANGER 25 BIG FAT COMMIT ANTI-PATTERN
110. use TDD style whenever tests pass, commit that makes you commit early and o!en
111. are you scared of using rebase? ANTIPATTERN DANGER 26 REBASE-FOBIA ANTI-PATTERN
112. rebase not to merge your unpushed commits with the fetched ones use pull with prepared by @lemiorhan rebase to get rebased commits from upstream safely use pull with REBASE feature branches to integrate into public branches that you pushed or that you pulled from another person Never use Rebase USE
113. do you know when we get conflicts and how to resolve it? ANTIPATTERN DANGER 27 CONFLICT-FOBIA ANTI-PATTERN
116. RECAP what was really happened at that time? LET’S
117. master TAG/v1.1 login HEAD DETACHED HEAD STATE $ git checkout cecd95914 Note: checking out 'cecd95914'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by performing another checkout. LIVING AT DETACHED HEAD STATE ANTI-PATTERN 28 ANTIPATTERN DANGER
118. master TAG/v1.1 login HEAD DETACHED HEAD STATE $ git rebase (and conflicts happen) $ git checkout HEAD~2 $ git checkout 43e3ab01 $ git checkout tags/v1.1 WHEN IT HAPPENS
119. master TAG/v1.1 login HEAD poor little developer...
120. master TAG/v1.1 login HEAD $ git checkout master
121. master TAG/v1.1 login HEAD $ git reflog aa67e3a2c HEAD@{0}: rebase finished: returning to refs/heads/fix/java-sql-Date-violates-LSR aa67e3a2c HEAD@{1}: rebase: fixes UnsupportedOperationException while calling toIstant() method of java.sql.Date a45f3c4e5 HEAD@{2}: rebase: checkout develop 630ddad6e HEAD@{3}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{4}: rebase: checkout develop 630ddad6e HEAD@{5}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{6}: pull: Fast-forward 8b59f8f50 HEAD@{7}: checkout: moving from fix/java-sql-Date-violates-LSR to develop
122. $ git reflog 630ddad6e the one we are searching for master TAG/v1.1 login HEAD aa67e3a2c HEAD@{0}: rebase finished: returning to refs/heads/fix/java-sql-Date-violates-LSR aa67e3a2c HEAD@{1}: rebase: fixes UnsupportedOperationException while calling toIstant() method of java.sql.Date a45f3c4e5 HEAD@{2}: rebase: checkout develop 630ddad6e HEAD@{3}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{4}: rebase: checkout develop 630ddad6e HEAD@{5}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{6}: pull: Fast-forward 8b59f8f50 HEAD@{7}: checkout: moving from fix/java-sql-Date-violates-LSR to develop
123. master typofix TAG/v1.1 login HEAD $ git branch typofix 630ddad6e
124. master typofix TAG/v1.1 login HEAD $ git branch typofix 630ddad6e KEEP CALM, NOTHING WILL BE LOST
125. LEMi ORHAN ERGiN agile software craftsman @ iyzico /lemiorhan lemiorhanergin.com @lemiorhan ANTIPATTERN DANGER