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

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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

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DISCLOSURE There is no formula for using git efficiently. Opinions are my own. It means the opposites might work perfectly for your conditions.

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git is powerful but you have to know using it properly

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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

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learn how git works no worries, I will cover how git behaves

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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

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Source Code Working Copy you want to version changes

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Source Code Working Copy $ git init Object Database .git Folder / Object Database Cache Staging Area / The Index initializing repo

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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

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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

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folder folder folder file file file $ git add . preparing commits

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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

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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

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$ 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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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are you sure? are you brave enough to jump to any commit ?

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do you have loooooong living topic branches ? ANTIPATTERN DANGER 3 LONG LIVING BRANCHES ANTI-PATTERN

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do you have loooooong living topic branches ? welcome to merge hell

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before merging do you validate commits back to source ? ANTIPATTERN DANGER code review, continuous integration, automated testing… 4 TOO LATE TO VALIDATE ANTI-PATTERN

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before merging do you validate commits back to source ? are you sure?

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merge and unmerge do you o!en want to just before releases ? ANTIPATTERN DANGER 5 CHERRY-PICK OBSSESSION ANTI-PATTERN

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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

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the commit graph ? do you fully understand ANTIPATTERN DANGER 6 DEATH ON COMMIT GRAPH ANTI-PATTERN

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the commit graph ? do you fully understand topic and shared branches, tracking branches, tags, HEADs, merge commits, reverted commits…

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Cure?

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Commit Early, Commit O"en Perfect Later, Publish Once

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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

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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

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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

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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

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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

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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

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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

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$ 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

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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

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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

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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

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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

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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

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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

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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

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stop adding prevent commits from being big ball of muds every change OMNIBUS BILL ANTI-PATTERN 10 ANTIPATTERN DANGER

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stop adding prevent commits from being big ball of muds every change local change sets at JetBrains IDEs

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stop adding every change partial add

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messages are read! # WHAT # (this commit will...) # 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

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messages are read! use git commit templates to create be"er commit messages com t m i

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by adding new commits ? do you rollback your mistakes ANTIPATTERN DANGER 12 MESS UP WITH THE ROLLBACK ANTI-PATTERN

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hard reset the merge commit $ git reset --hard HEAD~ if you haven't pushed yet HEAD MASTER Bug fıx

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never force push and change the history if you already pushed to shared branch Bug fıx HEAD MASTER

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revert the merge commit $ git revert 8f937c6 -m 1 if you already pushed Bug fıx HEAD MASTER

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is not the only method pushing commits to server ANTIPATTERN DANGER for sharing your code 13 CENTRALIZED GIT ANTI-PATTERN

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Git Pong Pairing $ git remote add personA $ 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

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with the ones in source branch ? how do you sync your commits ANTIPATTERN DANGER 14 MERGE FANATIC ANTI-PATTERN

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Bug fıx ladder pa!ern occurs when premature merge happens HEAD MASTER

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FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master

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FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master

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FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master

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FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master c5 REPLAY #1

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FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master c5 REPLAY #2 c6 c6

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FIX master c1 c2 c3 c4 c7 HEAD c5 c6 c5 c6 use rebase $ git rebase master c5 REWIND c6 c6

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FIX master c1 c2 c3 c4 c7 HEAD use rebase $ git rebase master c5 FINALIZE c6 c6

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deleting branches? are you scared of ANTIPATTERN DANGER 15 BRANCH CEMETERY ANTI-PATTERN

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wri!en in any form? anyone can push any code ANTIPATTERN DANGER 16 UNCONTROLLED POWER ANTI-PATTERN

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use pre-receive hooks

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Depend on each other Too many repositories ANTIPATTERN DANGER for sharing your code 17 WEB OF REPOSITORIES ANTI-PATTERN

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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

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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

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v1, v2, v3… having branch for every release ANTIPATTERN DANGER 18 ORACLE SYNDROME ANTI-PATTERN at the same time

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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

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to git repo you pushed confidential info ANTIPATTERN DANGER 19 WAITING FOR HACKERS ANTI-PATTERN

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Ref: https://help.github.com/articles/remove-sensitive-data/

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Do you know what evil merge is? ANTIPATTERN DANGER 20 EVIL MERGE ANTI-PATTERN

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No content

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do you use feature branches when there is no product at all ANTIPATTERN DANGER 21 BRANCH OVERDOSE ANTI-PATTERN

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use single branch topic branches simply make everything more complex

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Scared on using git commands ANTIPATTERN DANGER 22 CHUCKY THE COMMAND ANTI-PATTERN

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push add dosya güncelleme committed Track ediliyor untracked unmodiﬁed pushed modiﬁed staged Staging Alanında Local Repoda Uzak Repoda added add commit commit

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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

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h"ps://github.com/lemiorhan/git-kata

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no one knows git perfect do you suﬀer? ANTIPATTERN DANGER 23 NO HERO TO SAVE LIVES ANTI-PATTERN

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have a git-man at least one developer should expertise on git for supporting the others

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Having duplicate commits & Having irrelevant merge commits if you haven’t pushed yet ANTIPATTERN DANGER 24 DUPLICATE COMMITS ANTI-PATTERN

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No content

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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

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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

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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

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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

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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

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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:(

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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:(

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we commit when we have something big ANTIPATTERN DANGER 25 BIG FAT COMMIT ANTI-PATTERN

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use TDD style whenever tests pass, commit that makes you commit early and o!en

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are you scared of using rebase? ANTIPATTERN DANGER 26 REBASE-FOBIA ANTI-PATTERN

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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

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do you know when we get conﬂicts and how to resolve it? ANTIPATTERN DANGER 27 CONFLICT-FOBIA ANTI-PATTERN

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No content

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No content

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RECAP what was really happened at that time? LET’S

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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

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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

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master TAG/v1.1 login HEAD poor little developer...

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master TAG/v1.1 login HEAD $ git checkout master

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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

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$ 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

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master typofix TAG/v1.1 login HEAD $ git branch typofix 630ddad6e

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master typofix TAG/v1.1 login HEAD $ git branch typofix 630ddad6e KEEP CALM, NOTHING WILL BE LOST

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LEMi ORHAN ERGiN agile software craftsman @ iyzico /lemiorhan lemiorhanergin.com @lemiorhan ANTIPATTERN DANGER