Git Anti-Patterns - Extended Version With 28 Common Anti-Patterns) - SCTurkey Meetup

GIT ANTIPATTERNS

How To Mess Up With Git and Love It Again

LEMi ORHAN ERGiNAgile Software Craftsman, iyzico

/lemiorhan lemiorhanergin.com @lemiorhan

28 common git anti-patterns

DISCLOSUREThere is no formula for using git efficiently.

Opinions are my own. It means the opposites might work perfectly for your conditions.

GIT

git is powerfulbut you have to know using it properly

Are you using git

if all you do is commit-push-pulluse dropbox instead

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as if it is dropbox ?

1DROPBOX-ISH GIT ANTI-PATTERN

learn how git worksno worries, I will cover how git behaves

the way it keeps FILES & FOLDERS

working copy staging area

objects database repository

the way it keeps REFERENCESdirected acyclic graph keeping snapshots traversing graph branches, tags, heads

git has 2 mechanisms

Source CodeWorking Copy

you want to version changes


$ git init

Object Database.git Folder / Object Database

CacheStaging Area / The Index

initializing repo


$ git init --bare



RemoteUpstream Repo / Remote Repo

Server

initializing bare repo




Server


$ git add . preparing commits

folder

folder

folder

file

file

file





Server






Server


$ 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

folder

folder

folder

file

file

file

commit

$ git commit -m “second commit” commi!ing

folder

commit

branch

HEAD

folder

file

folder


folder

folder

folder

file

file

file

commit

$ git commit -m “third commit” commi!ing

folder

commit

folder

file

folder

folder

commit

branch

HEAD

file





Server






Server


$ git remote add origin http://upstream.repo$ git push -u origin master pushing to remote




Server


new changes from others are pushed




Server


$ git fetch fetching changes




Server


$ git merge FETCHED_HEAD updating working copy




Server


$ git pullgit fetch + git merge

ge!ing changes to source code




Server


want to update last commit




Server


$ 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

folder

folder

folder

file

file

file

commit

folder

commit

folder

file

folder

folder

commit

branch

HEAD

file



folder

folder

folder

file

file

file

commit

folder

commit

folder

file

folder

folder

commit

branch

HEAD

file






Server


want to squash or change last commits




Server


$ git reset --mixed mixed reseting

cannot be reached

entries for commits, files

and folders are removed from staging area




Server


want to get rid of last commits




Server


$ git reset --hard hard reseting

cannot be reached

removed from staging area

removed from working copy

are you brave enough tojump to any commit ?

jump to a branch

create a branch from a commit

create a branch from a tag

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$ git checkout feature/PA-121 $ git checkout -b fix/missing-sign-parameter 2449be8 $ git checkout -b hotfix/v1.1 tags/v1

2BROKEN TIME MACHINE ANTI-PATTERN

are you sure?

are you brave enough tojump to any commit ?

do you haveloooooong living

topic branches ?

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3LONG LIVING BRANCHES ANTI-PATTERN

do you haveloooooong living

topic branches ?

welcome tomerge hell

before mergingdo you validate commits

back to source ?

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code review, continuous integration, automated testing…

4TOO LATE TO VALIDATE ANTI-PATTERN

before mergingdo you validate commits

back to source ? are you sure?

merge and unmergedo you o!en want to

just before releases ?

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5CHERRY-PICK OBSSESSION ANTI-PATTERN

merge and unmergedo you o!en want to

just before releases ?

master

HEAD

TAG/v13

version 14

$ git cherry-pick Every-Single-Commit-We-Want-To-Deploy

the commit graph ?do you fully understand

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6DEATH ON COMMIT GRAPH ANTI-PATTERN

the commit graph ?do you fully understand

topic and shared branches, tracking branches, tags, HEADs, merge commits, reverted commits…

Cure?

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

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

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

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




master

HEAD

TOPIC

STEP 2

ORIGIN/master




master

HEAD

TOPIC

STEP 2

ORIGIN/master

if you branch is pushed already$ git push -f



to get forced pushes securely to rebase your commitsmaster

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

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

$ 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

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

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

Continuous Integration validates master branch continuouslymaster

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 GITmake 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

use terminalGUIs are prison balls of developers

it’s ok to use GUIs while checking diffs, resolving conflicts and viewing commit graph

BUTTON ADDICT ANTI-PATTERN7

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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-PATTERN8

ANTIPATTERN DANGER

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-PATTERN9

long living branches with carehandleANTIPATTERN DANGER

Squash all commits in your topic branch and make them available in working copy

long living branches with carehandle

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

stop adding

prevent commits from being big ball of mudsevery change

OMNIBUS BILL ANTI-PATTERN10

ANTIPATTERN DANGER

stop adding

prevent commits from being big ball of mudsevery change

local change sets at JetBrains IDEs

stop adding every changepartial add

messages areread!

# 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

comt

mi

F*CKING COMMIT MESSAGES ANTI-PATTERN11

ANTIPATTERN DANGER

messages areread!use git commit templates to create be"er commit messages

comt

mi

by adding new commits ?do you rollback your mistakes

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12MESS UP WITH THE ROLLBACK ANTI-PATTERN

hard reset the merge commit$ git reset --hard HEAD~

if you haven't pushed yet

HEAD

MASTER

Bug fıx

never force push and change the history

if you already pushed to shared branch

Bug fıx

HEAD

MASTER

revert the merge commit$ git revert 8f937c6 -m 1

if you already pushedBug fıx

HEAD

MASTER

is not the only methodpushing commits to server

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for sharing your code

13CENTRALIZED GIT ANTI-PATTERN

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

with the ones in source branch ?

how do you sync your commits

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14MERGE FANATIC ANTI-PATTERN

Bug fıx

ladder pa!ernoccurs when premature merge happens

HEAD

MASTER

FIX

master

c1 c2 c3 c4 c7

HEAD

c5 c6c5 c6

use rebase $ git rebase master

FIX

master

c1 c2 c3 c4 c7

HEAD

c5 c6c5 c6


FIX

master

c1 c2 c3 c4 c7

HEAD

c5 c6c5 c6


FIX

master

c1 c2 c3 c4 c7

HEAD

c5 c6c5 c6


c5

REPLAY #1

FIX

master

c1 c2 c3 c4 c7

HEAD

c5 c6c5 c6


c5

REPLAY #2

c6c6

FIX

master

c1 c2 c3 c4 c7

HEAD

c5 c6c5 c6


c5

REWIND

c6c6

FIX

master

c1 c2 c3 c4 c7

HEAD


c5

FINALIZE

c6c6

deleting branches?are you scared of

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15BRANCH CEMETERY ANTI-PATTERN

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

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

wri!en in any form?anyone can push any code

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16UNCONTROLLED POWER ANTI-PATTERN

use pre-receive hooks

Depend on each otherToo many repositories

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for sharing your code

17WEB OF REPOSITORIES ANTI-PATTERN

Mono Repository SystemEven 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

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

v1, v2, v3…having branch for every release

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18ORACLE SYNDROME ANTI-PATTERN

at the same time

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

to git repoyou pushed confidential info

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19WAITING FOR HACKERS ANTI-PATTERN

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

Do you know what evil merge is?

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20EVIL MERGE ANTI-PATTERN

do you use feature branches when there is no product at all

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21BRANCH OVERDOSE ANTI-PATTERN

use single branch topic branches simply make everything more

complex

Scared on using git commands

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22CHUCKY THE COMMAND ANTI-PATTERN

push

add

dosya güncelleme

committed

Track ediliyor

untracked unmodified pushedmodifiedstaged

Staging Alanında Local Repoda Uzak Repoda

added

add

commitcommit

hard reset

committed

Track ediliyor

untracked unmodified pushedmodifiedstaged

Staging Alanında Local Repoda Uzak Repoda

added

hard reset

hard reset

mixed reset

mixed reset

soft reset

rm --cached

rmx

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

no one knows git perfect do you suffer?

ANTIPATTERN DANGER

23NO HERO TO SAVE LIVES ANTI-PATTERN

have a git-man at least one developer should expertise on git

for supporting the others

Having duplicate commits &

Having irrelevant merge commits if you haven’t pushed yet

ANTIPATTERN DANGER

24DUPLICATE COMMITS ANTI-PATTERN

UPSTREAMLOCAL

master

c1 c2 c3 c4 c7

c5 c6c5 c6

FIX

HEAD

master

c1 c2 c3 c4 c7

c5 c6c5 c6

FIX

rebase and push

UPSTREAMLOCAL

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

HEAD

master

c1 c2 c3 c4 c7

c5 c6c5 c6

FIX

$ git rebase master

rebase and push

UPSTREAMLOCAL

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

HEAD

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

$ git push -f

rebase and push

UPSTREAMLOCAL

master

c1 c2 c3 c4 c7

c5 c6c5 c6

FIX

HEAD

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

pull rebased branch

UPSTREAMLOCAL

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

HEAD

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

$ git pull --rebase

pull rebased branch

UPSTREAMLOCAL

master

c1 c2 c3 c4 c7

c5 c6c5 c6

FIX

HEAD

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

c5 c6c5’ c6’

ORIGIN/FIX

$ git pull

pull rebased branch:(

UPSTREAMLOCAL

c1 c2 c3 c4 c7

c5 c6c5 c6

master

c1 c2 c3 c4 c7

c5 c6c5’ c6’

FIX

c5 c6c5’ c6’

c8

$ git pull

master

FIX

HEAD

ORIGIN/FIX

pull rebased branch:(

we commit when we have something big

ANTIPATTERN DANGER

25BIG FAT COMMIT ANTI-PATTERN

use TDD style whenever tests pass, commit

that makes you commit early and o!en

are you scared of using rebase?

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26REBASE-FOBIA ANTI-PATTERN

rebasenot to merge your unpushed

commits with the fetched ones

use pull with

prepared by @lemiorhan

rebaseto get rebased commits from upstream safely

use pull with

REBASEfeature branches to integrate

into public branches

that you pushed or that you pulled

from another person

Never use Rebase

USE

do you know when we get conflicts and how to resolve it?

ANTIPATTERN DANGER

27CONFLICT-FOBIA ANTI-PATTERN

RECAP

what was reallyhappened at that time?

LET’S

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-PATTERN28

ANTIPATTERN DANGER

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

master

TAG/v1.1

login

HEAD

poor little developer...

master

TAG/v1.1

login

HEAD

$ git checkout master

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 630ddad6e HEAD@{8}: rebase: updating HEAD

$ git reflog

630ddad6ethe 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 630ddad6e HEAD@{8}: rebase: updating HEAD

master

typofix

TAG/v1.1

login

HEAD

$ git branch typofix 630ddad6e

master

typofix

TAG/v1.1

login

HEAD

$ git branch typofix 630ddad6e

KEEP CALM, NOTHING WILL BE LOST

LEMi ORHAN ERGiNagile software craftsman @ iyzico

/lemiorhan lemiorhanergin.com @lemiorhan

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