Transformative Git Practices

@durdn#DevoxxPL
Platinum Sponsors:
Transformative Git Practices
Nicola Paolucci
New Techniques for Hyper-productivity

Today we’ll cover some powerful Git goodies
Worktree clones Painless sub-projectsThe magic of --fixup
For when you have to
work concurrently on
multiple long running
branches
You can use git subtree
to handle external
libraries in a clean and
efficient way
A powerful technique to
cleanup your history
before sharing with it the
team
and a final, cool topic…

@durdn
Git Worktree
Local clones for parallel work

The old simple way: branch, commit, push
master
HEAD
HEAD
new-feature
git checkout -b new-feature
Uns

@durdn
It’s clumsy to work in parallel
on multiple branches

Or are a pro at using
the Stash (which is
cool btw)
You either work
around it having
intermediate WIP
commits
It leaves hanging
uncommitted work
lying around
To work on 2+ branches at the same time

@durdn
git stash is awesome
It’s a way to temporarily store your unsaved work
on a stack of patches
stash@{0}
stash@{1}
stash@{2}
stash@{3}
git stash save

@durdn
But there’s a new way: git worktree
Available since Git 2.5

git worktree creates additional clones inside your project
Add a new worktree
git worktree add
-b feature/PRJ-1-new-fancy-button
fancy-button
Branch to checkout in clone
Folder where to checkout

It shows the folder
git worktree list - shows the worktrees created
And the branch is pointing at
Where the additional cloned has
been checked out
So that you have an immediate
overview of all the trees you have
created
git worktree list$
/Users/np/p/dac f1f7f8b [master]
/Users/np/p/dac/git-the-all-new-modern-workflow 7fe9096 [blog/git-…-new-modern-workflow]
/Users/np/p/dac/provision-a-cluster-with-rancher b4b84fb [blog/provision-…-with-rancher]
/Users/np/p/dac/static-site-with-pipelines-and-middleman d6bd9fd [blog/static-site-…-middleman]

git worktree prune - once you’re done with a clone
git worktree prune$
rm -rf fancy-button$

Demo Time!
Let’s see how “git worktree” works in
practice

Replace the normal branching?Keep working while testingBetter work in parallel
Why git worktree is a great choice
Having multiple clones
with all the branches
you’re working on
available in your repo is
a big win.
If you have a big battery
of tests which are slow
to run, you can run them
in a worktree clone while
you keep working.
When you get used to
worktrees, they become
very natural for any
feature branch work.

@durdn
The magic of --fixup
Smooth history cleanup for perfectionists

@durdn
It’s great to work in small chunks

@durdn
There’s a tension between…

Commits as
throw away
save points
Commits as a
polished
meaningful way
to communicate
a feature

@durdn
There’s a way to square the circle

@durdn
Helps you clean up your private branches
before publishing them interactively
What is an
--interactive rebase?
master
feature

First step: Turn on the “autosquash” feature
git config --global rebase.autosquash true$

@durdn
Work in small throwaway bits, use
commits as save points
as you please

Fixup
Annotate your raw commits with “--fixup” or “--squash”
Squash
Use ﬁxup to quickly ﬁx
problems in a commit,
without the need to change
or add to the commit
message
For additions to a commit
where you want to add also
an additional note to the
commit message
git commit --fixup <commit>$
git commit --squash -m”Add to feature” <commit>$

Fixup
Annotate your raw commits with “--fixup” or “--squash”
Squash
Use ﬁxup to quickly ﬁx
problems in a commit,
without the need to change
or add to the commit
message
For additions to a commit
where you want to add also
an additional note to the
commit message
git commit --fixup :/<string pattern>$
git commit --fixup :/PRJ-123$

@durdn
Rebase is now pre-filled and easy

Demo Time!
Let’s see how “--fixup” and “--squash” work
in practice

Let’s talk about project dependencies

git subtree
Extract project
Alternative to git submodule to handle
external dependencies.
Inject dependency
It allows you to inject an external
project into a sub-folder
Introduced in 1.7.11
It can be also used to extract a
sub-folder as separate project

Clean integration pointsStores in regular commitsNo training
When and why is git subtree a great choice
Does not require your
entire team to be trained
in the use of the
command
The command stores
the external
dependency in regular
Git commits. Squashing
the history optionally.
It makes it easy to see
when integrations
happened and makes it
easy to revert them.

Syntax to inject a project
Command to inject project
git subtree add
--prefix target-folder
https://bitbucket.org/team/sub.git
master --squash
Folder where to insert code
Repository URL
v1.1

Under the hood of git subtree
commit ab54c4e0b75c3107e3e773ab9b39268abddca002
Author: Nicola Paolucci <npaolucci@atlassian.com>
Date: Tue Sep 29 15:27:35 2015 +0200
Squashed ‘src/sub-project‘ content from commit df563ed
git-subtree-dir: src/sub-project
git-subtree-split: df563ed15fa6…6b2e95d3

Result of git subtree add
commit 8fb507baf7b270c30c822b27e262d0b44819b4c5
Merge: 606cd3e ab54c4e
Date: Tue Sep 29 15:27:35 2015 +0200
Merge commit 'ab54c4e0b75c3107e3e773ab9b39268abddca002' as '.vim/bundle/fireplace'
commit ab54c4e0b75c3107e3e773ab9b39268abddca002
Date: Tue Sep 29 15:27:35 2015 +0200
Squashed '.vim/bundle/fireplace/' content from commit df563ed
git-subtree-dir: .vim/bundle/fireplace
git-subtree-split: df563ed15fa685ce2508bf16b3ca7e176b2e95d3

To keep the sub-project up to date
git subtree pull
--prefix target-folder
https://bitbucket.org/team/sub.git
master --squash
Command to pull project
Folder where to insert code
Repository URL
v1.5

Find the symbolic ref matching a hash (sha-1)
sha-1 of last commit pulled
Git plumbing to list all remote refs
Repository URL
git ls-remote https://bitbucket.org/team/sub.git | grep df563ed
df563ed15fa685ce2508bf16b3ca7e176b2e95d3 v1.1
5eaff1232acedeca565er7e1333234dacccebfff v1.5
git ls-remote https://bitbucket.org/team/sub.git | grep <sha-1>

Aliases to make your life easier!
[alias]
sba = "!f() { git subtree add --prefix $2 $1 master --squash; }; f"
sbu = "!f() { git subtree pull --prefix $2 $1 master --squash; }; f"
Alias section of your .gitconfig
http://bit.do/git-aliases

How to use the aliases
git sba <repo URL> <destination-folder>
git sba https://bitbucket.org/team/sub.git src/sub

When everyone in the
team must work on
sub-projects
When you have
constant updates to
your dependencies
When you have many
dependencies
When NOT to use git subtree

@durdn
For complex project dependencies
Use a dependency tool.
Really.

Alternatives?
Read my rant
on project
dependencies
http://bit.do/git-dep

@durdn
How to extract a project
Let’s learn how to use subtree split

Git subtree to extract a project
Command to split out project
git subtree split
--prefix my/project/
--branch extracted
Folder prefix to extract
where we store it

Push to new remote
We can remove the contents of the
folder from the repo
Import extracted branch
Initialise a new repo and import the
extracted branch
Remove from old repo
After we imported the code we can
push it to a new repository
git rm -rf my/project
git init
git pull ../path/ extracted
git remote add origin …
git push origin -u master

@durdn
Have a Pipeline with your repo
Build your project in the cloud

• Big cool statistic
• 2,56
9
• Add-Ons in Marketplace

Deploy to any of these and more!
…

NICOLA PAOLUCCI • ATLASSIAN • @DURDN
Twitter: @durdn
http://bit.do/pipelines

We’ve covered some powerful Git goodies
Worktree clones Painless sub-projectsThe magic of --fixup
For when you have to
work concurrently on
multiple long running
branches
You can use git subtree
to handle external
libraries in a clean and
efficient way
A powerful technique to
cleanup your history
before sharing with it the
team

NICOLA PAOLUCCI • ATLASSIAN • @DURDN
Twitter: @durdnhttp://bit.do/pipelines
Thank you! Follow me @durdn

Transformative Git Practices

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