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LEMi ORHAN ERGiNagile software craftsman @ iyzico
GIT ANTIPATTERNS
How To Mess Up With Git and Love It Again
/lemiorhan lemiorhanergin.com @lemiorhan
meetup.scturkey.org agileturkey.org
dev.iyzipay.com
GIT
LEMi ORHAN ERGiNagile software craftsman @ iyzico
agile practice lead at iyzico developing software since 2001
worked at Sony, eBay/GittiGidiyor, ACM consultant, architect, mentor, developer
founder of Software Craftsmanship Turkey ex community leader of Agile Turkey
git is powerfulbut you have to know using it properly
Are you using git
if all you do is commit-push-pulluse dropbox instead
ANTIPATTERN DANGER
as if it is dropbox ?
learn how git worksno worries, I will cover how git behaves
the way it keeps FILES & FOLDERSworking 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
Source CodeWorking Copy
you want to version changes
Source CodeWorking Copy
$ git init
Object Database.git Folder / Object Database
CacheStaging Area / The Index
initializing repo
Source CodeWorking Copy
$ git init --bare
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
initializing bare repo
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git add . preparing commits
folder
folder
folder
file
file
file
$ git add . preparing commits
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git add . preparing commits
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git commit -m “initial commit” commi!ing
$ 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 “initial commit” commi!ing
folder
commit
branch
HEAD
folder
file
folder
For more details, refer to book Git Internals by Scott Chacon
folder
folder
folder
file
file
file
commit
$ git commit -m “initial commit” commi!ing
folder
commit
folder
file
folder
folder
commit
branch
HEAD
file
For more details, refer to book Git Internals by Scott Chacon
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git commit -m “initial commit” commi!ing
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git remote add origin http://upstream.repo$ git push -u origin master pushing to remote
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
new changes from others are pushed
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git fetch fetching changes
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git merge FETCHED_HEAD updating working copy
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git pullgit fetch + git merge
ge!ing changes to source code
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
want to update last commit
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git reset --soft $ git commit --amend/ so" reseting
cannot be reached
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
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
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
want to squash or change last commits
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ git reset --mixed mixed reseting
cannot be reached
removed from staging area
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
want to get rid of last commits
Object Database.git Folder / Object Database
CacheStaging Area / The Index
RemoteUpstream Repo / Remote Repo
Server
Source CodeWorking Copy
$ 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
ANTIPATTERN DANGER
$ git checkout feature/PA-121 $ git checkout -b fix/missing-sign-parameter 2449be8 $ git checkout -b hotfix/v1.1 tags/v1
are you sure?
are you brave enough tojump to any commit ?
do you haveloooooong living
topic branches ?
ANTIPATTERN DANGER
do you haveloooooong living
topic branches ?
welcome tomerge hell
before mergingdo you validate commits
back to source ?
ANTIPATTERN DANGER
code review, continuous integration, automated testing…
before mergingdo you validate commits
back to source ? are you sure?
merge and unmergedo you o!en want to
just before releases ?
ANTIPATTERN DANGER
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
ANTIPATTERN DANGER
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 single 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
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
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
always pull with rebase
$ git pull --rebase origin master
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
Any Other Cures?
use terminalGUIs are prison balls of developers
it’s ok to use GUIs while checking diffs, resolving conflicts and viewing commit graph
do not losetake 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
TOPIC
HEAD
MASTER
long living branches with carehandle
Squash all commits in your topic branch and make them available in working copy
$ 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
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
stop adding
prevent commits from being big ball of mudsevery change
local change sets at intelliJ
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
.git-commit-template.txt
use git commit templates to create be"er commit messages
comt
mi
messages areread!use git commit templates to create be"er commit messages
comt
mi
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.
master
TAG/v1.1
login
HEAD
DETACHED HEAD STATE
(login)$ git rebase master First, rewinding head to replay your work on top of it... Applying: settings Using index info to reconstruct a base tree... Falling back to patching base and 3-way merge... Auto-merging settings CONFLICT (add/add): Merge conflict in settings error: Failed to merge in the changes. Patch failed at 0001 settings The copy of the patch that failed is found in: .git/rebase-apply/patch
(a16e6e8)$
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
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 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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