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Git Workflows A-la-carte, Presenation at jdays2013 www.jdays.se by Nicola Paolucci
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Workflows á-la-carte
Nicola PaolucciDeveloper Advocate / Git Evangelist
@durdndurdn.comI come out nice in pictures, I know :-).
Cheap local branchingFull local history
Speed
Staging area
prominent in Open Source
Huge community
You heard has
Feature based workflow
10x the speed of svn
Distributedcryptographic integrity
ground breaking paradigm is ground breaking
Workflow building blocks
rebasepowerful merging
fork
clone
cheap branching
distributed
RELEASECan we fix a bug for the
upcoming?
FEATUREIs the code for that
complete?
BUILDCan we
the current code ?
REVIEWEDHas everybody
the code for this feature ?
HOTFIXCan we do a fast
for the current release?
Practices & Decisions
1
2
What we’ll cover:
Branching models
Tooling & Automation3
4 Continuous Integration
Which branching model?1
Product Releases
1 Continuous Delivery
2
Two common Branching Models
1.1 for Continuous Delivery
Tim
emaster/
productionstagingfeature
master is in production
staging is the next version
new features off staging
with branch names like: username/ISSUE-KEY-summary
promoted from staging, can receive hotfixes
Hotfix
PR
for Product Releases1.2
One Central Repository1
One Branch per Feature
One Branch per Bugfix
2
3
Tim
emasterfeature
branches
PRJ-
123-
desc
ript
ion
Tim
emasterbugfix
branch
PRJ-
123-
bug-
desc
ript
ion
Release Branches4
master is alpha / RC5
Long running
Tim
emasterrelease
branch
PRJ-
345-
bug-
desc
ript
ion
bugfix
2.2
Automatic merges for the win!
PRJ-
345-
bug-
desc
ript
ion
Tim
e
release branch
master
2.2
release branch
bugfix
2.1
Automatic MERGES!
Placeholder for changes you DON’T want to merge!
release branch
2.2
release branch
2.1
2.1.4
2.2.1
We don’t want to merge the 2.1.x version!
2.1.5-SNAPSHOT
What can we do here?
git merge --strategy= ours
stable branch
2.2
stable branch
2.1
2.1.4
2.2.1
2.1.5-SNAPSHOT
merge commit, content discarded$> git checkout stable-2.2
$> git merge -s ours stable-2.1
Deep breath, it’s really simple
The merge protocolThe secret sauce
Release branch
The merge protocolThe secret sauce
When a branch is: Change flows from branch to baseline:
Change flows from baseline to branch:
More stable than its baseline Continuously Never
Less stable than its baseline When code complete Continuously
Release branch
Release branch
Feature branchesCredit: Laura Wingerd - The Flow of change
The merge protocolThe secret sauce
Release branch
Release Branch
Master
Merge continuously
Backport single changes using git cherry-pick
Never merge!
Practices & Decisions2
turbo boost!
What is a Pull Request?
Hey I have some code I want to merge here,
take a look?
Low friction collaboration
Pull Request
I have some code here!
Can I merge it here?
Does a debate even exist?
Merge vs Rebase
MER
GE REBA
SE
master
feature
What is a Rebase?Merge commit
master
feature
Traceability1
At a cost: readability2
3
Merge as team policy
bisect debugging is harder
with no fast-forwards
History flat and clean1
Delicate with Pull Requests
Dangerous for unexperienced
2
3
Rebase as team policy [1]
Re-resolve similar conflicts4
Requires often a force push
Loses context for feature
5
6
Rebase as team policy [2]
Do it1
Do it
Do it!!!!!!
2
3
Rebase as a local cleanup
git rebase --interactive
If team unfamiliar, don’t rebase1
Encourage rebase as cleanup2
Recommendation?
and proper ecology
Don’t fear the Merge! Use it!3
May rebase feature branches
Work with the tool!
4
5
Recommendation?
git log --first-parent
Trying to strive for a linearized history is less useful than you think
To update the feature branch
Explicit merges into the mainline
After review!
Single Repository vs
Remote Forks
Every one has their remote repository
With Forks
Full remote copy, each has one Integrator, Gatekeeper,
Tech Lead, etc.
Complete visibility1
No per Dev remotes required
KISS
2
3
Pros of a Single RepoAll feature branches available
Forks Are Great too BTW
FORKING IN THE
ENTERPRISE
FORKING IN
ENTERPRISE5 Reasons for...
REASON 1
Great for customizing librariesand still get bug fixes
REASON 2
Great for innovation spikesand maybe add it later
FORKING IN
ENTERPRISE
REASON 3
Protecting your components
but still be open for changes
FORKING IN
ENTERPRISE
REASON 4
Reduce the noise
and keep the overview for huge projects
FORKING IN
ENTERPRISE
REASON 5
Interaction with Contractors & Interns
protect your sources
FORKING IN
ENTERPRISE
Tooling & Automation3
Hooks
Hooks are little scripts you can place in
the `$GIT_DIR/hooks` directory to trigger
action at certain points.
– githooks Documentation
”“
Pre Post
Local Remote
Local Remotepre-receiveupdatepost-receivepost-update
pre-/post-applypatchpre-/post-commit
pre-rebasepost-checkout
post-mergepre-push
Code Quality via pre-commit hooks
.git/hooks/pre-commit!
git add -u!git commit -m "TEST checkstyle"!
Starting audit...!!
/Users/user/[...]/com/atlassian/stash/web/projects/ProjectController.java:161:12: 'for' is not followed by whitespace.!!
Audit done.!Commit aborted.
Branch from green builds
.git/hooks/post-checkout
$ git checkout master!master is lookin'good! !c4f3b4b has 4 green builds.! !$ git checkout stable-2.3 !DANGER! stable-2.3 is busted. e1324fa has 2 red builds.!
Get it at: bitly.com/green-builds
4 What happens to CI with ?
What happens to CI with git?1
An explosion of branches2
3 Performance degradation of build sys
Building everything is expensive1
Automatically build stable and master2
3 Manually trigger feature branch builds
In Conclusion: the recipe
!!!
!!!!!
Branching Model
Practices & Decisions
Automation & CI setup
Conclusions
!!!!!
Product workflow
Continuous delivery workflow
Embrace PR
Build automatically,
but leave knobs!Single Repo
or Forks
!!!
Collaboration Model
Centralized
Hooks, hooks everywhere
Merge vs Rebase
Nicola PaolucciTHANK YOU FOR YOUR ATTENTION!
@durdndurdn.comShould I change the pic? ;-)
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