NICOLA PAOLUCCI • DEVELOPER INSTIGATOR • • @DURDN

The business case for GitConcepts and techniques to convert you

into a master of the DVCS craft

Becoming a Git Master

I'm George. George McFly. I'm your density… I mean,

your destiny

Let’s Become Git Pros!

C O N F L I C T R E S O L U T I O N T I P S

H I D I N G S T U F F

Here you’ll learn:

P O L I S H Y O U R C O D E

P R E V E N T TA M P E R I N G

P R O J E C T D E P E N D E N C I E S

P R O A L I A S E S & P R O M P T

A pro command prompt

P R O A L I A S E S & P R O M P T

Everyone has their favorite, but!Liquid prompt is awesome

http://bit.do/liquid-prompt

P R O A L I A S E S & P R O M P T

Everyone has their favorite, but!Liquid prompt is awesome

http://bit.do/liquid-prompt

Crafting Awesome Aliases

Aliases are stored in .gitconfig

In a section prefixed: [alias]

P R O A L I A S E S & P R O M P T

Basic Alias FormVery simple:

ls = log --oneline

[vagrant@vagrant-ubuntu-trusty-64:/home/vagrant/buildstep] master ± git ls 90aa814 Merge pull request #85 from marqu3z/master f1eb16b overwrite source.list e6b9d16 change repo before prepare task 8bc10c0 Fix for deprecated repository e34d861 Link to buildpacks.txt instead 4502635 Merge pull request #76 from elia/fix-72-no-buildpack-bundle-install 38be796 Bundle install ain't needed against the buildpack

P R O A L I A S E S & P R O M P T

You can do great things with just this

For example: amend the last commit with everything I have here uncommitted and new

caa = commit -a --amend -C HEAD

You can’t pass parameters to simple aliases :(

Or can you?!

muahahhahahhahahahahahahahahhahahahhahahahah!

P R O A L I A S E S & P R O M P T

For multiple commands or complex parameters use a bash function!

You can escape to a shell with ! like this:

my_alias = "!f() { <command> }; f”

P R O A L I A S E S & P R O M P T

Some useful shortcuts and variablesMore in any bash manual

$@ - all command line parameters passed

$1 - first command line parameter

$2 - second command line parameter

Ma, it’s the mini-DSL I always wanted!

P R O A L I A S E S & P R O M P T

What can you do with this?Cool cool things, for example add a Bitbucket remote:

git remote add $1 https://bitbucket.org/$2.git;

P R O A L I A S E S & P R O M P T

ra = "!f() { \ \ }; f"

What can you do with this?Cool cool things, for example add a Bitbucket remote:

git remote add $1 https://bitbucket.org/$2.git;

P R O A L I A S E S & P R O M P T

ra = "!f() { \ \ }; f"

What can you do with this?Cool cool things, for example add a Bitbucket remote:

git remote add $1 https://bitbucket.org/$2.git;

git ra jsmith jsmith/prj

P R O A L I A S E S & P R O M P T

ra = "!f() { \ \ }; f"

What can you do with this?Cool cool things, for example add a Bitbucket remote:

git remote add $1 https://bitbucket.org/$2.git;

git ra jsmith jsmith/prj

P R O A L I A S E S & P R O M P T

Get all the alias goodness on Bitbuckethttp://bit.do/git-aliases

© http://www.amigosdosbichos.org/

1. Powers of invisibility

© http://www.amigosdosbichos.org/

1. Powers of invisibility

Tell git which files or folders to ignore

in .gitignore

What if the file is already committed?!

muahahhahahhahahahahahahahahhahahahhahahahah!

Hide files fromDifferent from .gitignore, it hides committed files

P O W E R S O F I N V I S I B I L I T Y

git update-index --assume-unchanged <file>

very useful with git-svn

Hide files fromRevert it with:

P O W E R S O F I N V I S I B I L I T Y

git update-index --no-assume-unchanged <file>

remember to add --no

P O W E R S O F I N V I S I B I L I T Y

List assumed unchanged files

git ls-files -v | grep ^hUseful as alias (see alias list from before)

Conflict Resolution Tips

What is a conflict?

P R O A L I A S E S & P R O M P T

A word on terminology

Current checked out branch

--ours

What do ours and theirs mean when solving conflicts?

Commit coming in (i.e. via merge)

--theirs

P R O A L I A S E S & P R O M P T

Basics for easy conflict resolutionThe common commands are:

$ git checkout --ours/--theirs <file> Check back out our own/their own version of the file

$ git add <file> Add the change to the index will resolve the conflict

P R O A L I A S E S & P R O M P T

Aliases for easy conflict resolutionAdd these to [alias] in .gitconfig:

git checkout --ours $@ && git add $@;

P R O A L I A S E S & P R O M P T

Aliases for easy conflict resolutionAdd these to [alias] in .gitconfig:

ours = "!f() { \ \ }; f" git checkout --ours $@ && git add $@;

P R O A L I A S E S & P R O M P T

rerere resolve!Reuse Recorded Resolution will help you when dealing with repetitive and similar merge conflicts.

$ git config --global rerere.enabled true Turns it on and forget about it

P R O A L I A S E S & P R O M P T

Sample output rerere

$ git add hello.rb $ git commit Recorded resolution for 'hello.rb'. [master 68e16e5] Merge branch 'i18n'

Auto-merging hello.rb CONFLICT (content): Merge conflict in hello.rb Resolved 'hello.rb' using previous resolution.

Cover your tracks(aka polish your code)

P O L I S H Y O U R C O D E

What is a rebase?It’s a way to replay commits, one by one,

on top of a branch

MASTER

FEATURE

P O L I S H Y O U R C O D E

What is a rebase?It’s a way to replay commits, one by one,

on top of a branch

MASTER

FEATURE

P O L I S H Y O U R C O D E

What is a rebase?It’s a way to replay commits, one by one,

on top of a branch

MASTER

FEATURE

Don’t use!

P O L I S H Y O U R C O D E

What is a rebase?Correct way to use rebase to update a

feature branch

MASTER

FEATURE

P O L I S H Y O U R C O D E

What is a rebase?Correct way to use rebase to update a

feature branch

MASTER

FEATURE

P O L I S H Y O U R C O D E

What is an --interactive rebase?It’s a way to replay commits, one by one,

deciding interactively what to do with each

PICK

SQUASH

REWORD

FIXUP

EDIT

EXEC

P O L I S H Y O U R C O D E

--autosquashAutomatically modify the todo list of

rebase --interactive by annotating commits

$ git config --global rebase.autosquash true Turns on the feature

P O L I S H Y O U R C O D E

--autosquashYou can prepend commit messages with:

git commit -m “squash! …"

git commit -m “fixup! …"

git commit -m “reword! …"

etc…

Rebase task list will be then prepopulated

CUSTOMARY WARNING!

rebase rewrites history!

Treat this power with great care. Only rewrite history of local branches or…

Prevent tampering

Always a balancing act

Security DevSpeed

P R E V E N T TA M P E R I N G

Lock down your repo

# no rewriting history denyNonFastForwards = true

# no deleting history denyDeletes = true

# check object consistency fsckObjects = true

Edit .git/config in the [receive] section:

Reject force push,Git project has already an update hook ‘update-paranoid’ that is designed to

reject history rewriting updates

Luke

http://bit.do/update-paranoid

Reject force push,Luke

Reject force push,Luke

P R E V E N T TA M P E R I N G

Impersonating Authors is easy with

$ git commit -m "I'm Luke" $ git commit --author "Elvis <elvis@graceland.net>" -m "I'm elvis" commit a9f0967cba236465d6cb68247.. Author: Elvis <elvis@graceland.net> Date: Mon Apr 22 18:06:35 2013 -0500

I'm Elvis

commit d6eb7572cbb4bdd8e2aaa5c90.. Author: Luke <luke@tatooine.com> Date: Mon Apr 22 18:04:54 2013 -0500

I'm Luke

P R E V E N T TA M P E R I N G

Solution: you can sign & verify tags

git tag -s <tag_name> -m “message”Sign a tag with your GPG key

git tag -v <tag_name>Verifies that the signature is valid

Signing release tags is often all you need

P R E V E N T TA M P E R I N G

Aside on GPGThe GNU Privacy Guard

GnuPG allows to encrypt and sign your data and communication, features a versatile key management system.

P R E V E N T TA M P E R I N G

Harden up by signing thingsSample gpg commands to get you started:

gpg --gen-keyGenerate your GPG keys

gpg -kList your keys

gpg -a --export <keyid>Export your key

P R E V E N T TA M P E R I N G

Hide files in raw objects

actually writes into the object db

git hash-object -w <file>

Remember to associate a tag to it or it will be garbage collected

P R E V E N T TA M P E R I N G

Store your signature in Simple! Add a tag referencing your public key

gpg -a --export <keyid> | \ git hash-object -w --stdin

Store your public key in a raw object

git tag nicks-key 65704f3…Tag the raw object with a label

raw object id

P R E V E N T TA M P E R I N G

Import other public keys

git cat-file -p tims-key | gpg --import

Import a GPG key from a tag

P R E V E N T TA M P E R I N G

Now you can sign & verify tags

git tag -s <tag_name> -m “message”Sign a tag with your GPG key

git tag -v <tag_name>Verifies that the signature is valid

and Project Dependencies

How do you handle project dependencies

with ?

Splitting up a project is painful, for so many

reasons

Use a build/dependency tool instead of

G I T A N D P R O J E C T D E P E N D E N C I E S

I’ll give you an incomplete list of examples!

Java

Nodejs

Javascript

Python Pip easy-install

Ruby

G I T A N D P R O J E C T D E P E N D E N C I E S

I’ll give you an incomplete list of examples! (2)

C#

C++ c-make

Objective C

PHP

Go godep

Another possibility: use git submodule

Another possibility: use git subtree

Use other build and cross-stack

dependency tools

G I T A N D P R O J E C T D E P E N D E N C I E S

•Android Repo (http://bit.do/android-repo)•Repobuild (chrisvana / repobuild)•Chromium depot_tools (http://bit.do/depot-tools)•Facebook Buck (http://facebook.github.io/buck/)•Twitter Pants (http://bit.do/twitter-pants)

For example you can check out:

P R O A L I A S E S & P R O M P T

Review these ideas onlinehttp://bit.do/git-deps

C O N F L I C T R E S O L U T I O N T I P S

H I D I N G S T U F F

Today we covered:

P O L I S H Y O U R C O D E

P R E V E N T TA M P E R I N G

P R O J E C T D E P E N D E N C I E S

P R O A L I A S E S & P R O M P T

NICOLA PAOLUCCI • DEVELOPER INSTIGATOR • ATLASSIAN • @DURDN

Thank you!

Mechelen - 26th November

@durdn