This document provides tips and techniques for becoming a Git master, including: 1. Creating aliases to simplify common Git commands like committing and adding remotes. Aliases allow parameters and bash functions for complex commands. 2. Using features like assume-unchanged to hide files from Git and rerere to automate resolving similar conflicts. 3. Interactive rebasing to polish commit histories by squashing, rewording, and fixing up commits. Rebasing rewrites history so care is needed. 4. Techniques for preventing history tampering like reject force pushes and signing tags for verification. GPG keys can be stored and imported in Git. 5. Handling project dependencies with build tools or

1. NICOLA PAOLUCCI • DEVELOPER INSTIGATOR • • @DURDN
The business case for Git
Concepts and techniques to convert you
into a master of the DVCS craft
Becoming a Git Master

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

3. Let’s Become Git Pros!

4. CONFLICT RESOLUTION TIPS
HIDING STUFF
Here you’ll learn:
POLISH YOUR CODE
PREVENT TAMPERING
PROJECT DEPENDENCIES
PRO ALIASES & PROMPT

5. A pro command prompt

6. PRO ALIASES & PROMPT
Everyone has their favorite, but!
Liquid prompt is awesome
http://bit.do/liquid-prompt

7. PRO ALIASES & PROMPT
Everyone has their favorite, but!
Liquid prompt is awesome
http://bit.do/liquid-prompt

8. Crafting Awesome Aliases

9. Aliases are stored in
.gitconfig

10. In a section prefixed:
[alias]

11. PRO ALIASES & PROMPT
Basic Alias Form
Very 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

12. PRO ALIASES & PROMPT
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

13. You can’t pass parameters
to simple aliases :(

14. Or can you?!

15. muahahhahahhaha
hahahahahahahha
hahahhahahahah!

16. PRO ALIASES & PROMPT
For multiple commands or complex
parameters use a bash function!
You can escape to a shell with ! like this:
my_alias = "!f() { <command> }; f”

17. PRO ALIASES & PROMPT
Some useful shortcuts and variables
More in any bash manual
$@ - all command line parameters passed
$1 - first command line parameter
$2 - second command line parameter

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

19. PRO ALIASES & PROMPT
What can you do with this?
Cool cool things, for example add a Bitbucket remote:
git remote add $1 https://bitbucket.org/$2.git;

20. PRO ALIASES & PROMPT
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;

21. PRO ALIASES & PROMPT
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

22. PRO ALIASES & PROMPT
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

23. PRO ALIASES & PROMPT
Get all the alias goodness on Bitbucket
http://bit.do/git-aliases

24. © http://www.amigosdosbichos.org/
1. Powers of invisibility

25. © http://www.amigosdosbichos.org/
1. Powers of invisibility

26. Tell git which files
or folders to ignore
in .gitignore

27. What if the file is
already committed?!

28. muahahhahahhaha
hahahahahahahha
hahahhahahahah!

29. Hide files from
Different from .gitignore, it hides committed files
POWERS OF INVISIBILITY
git update-index --assume-unchanged <file>
very useful with git-svn

30. Hide files from
Revert it with:
POWERS OF INVISIBILITY
git update-index --no-assume-unchanged <file>
remember to add --no

31. POWERS OF INVISIBILITY
List assumed unchanged files
git ls-files -v | grep ^h
Useful as alias (see alias list from before)

32. Conflict Resolution Tips

33. What is a conflict?

34. PRO ALIASES & PROMPT
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

35. PRO ALIASES & PROMPT
Basics for easy conflict resolution
The 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

36. PRO ALIASES & PROMPT
Aliases for easy conflict resolution
Add these to [alias] in .gitconfig:
git checkout --ours $@ && git add $@;

37. PRO ALIASES & PROMPT
Aliases for easy conflict resolution
Add these to [alias] in .gitconfig:
ours = "!f() {
}; f"
git checkout --ours $@ && git add $@;

38. PRO ALIASES & PROMPT
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

39. PRO ALIASES & PROMPT
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.

40. Cover your tracks
(aka polish your code)

41. POLISH YOUR CODE
What is a rebase?
It’s a way to replay commits, one by one,
on top of a branch
MASTER
FEATURE

42. POLISH YOUR CODE
What is a rebase?
It’s a way to replay commits, one by one,
on top of a branch
MASTER
FEATURE

43. POLISH YOUR CODE
What is a rebase?
It’s a way to replay commits, one by one,
on top of a branch
MASTER
FEATURE
Don’t use!

44. POLISH YOUR CODE
What is a rebase?
Correct way to use rebase to update a
feature branch
MASTER
FEATURE

45. POLISH YOUR CODE
What is a rebase?
Correct way to use rebase to update a
feature branch
MASTER
FEATURE

46. POLISH YOUR CODE
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

47. POLISH YOUR CODE
--autosquash
Automatically modify the todo list of
rebase --interactive by annotating commits
$ git config --global rebase.autosquash true
Turns on the feature

48. POLISH YOUR CODE
--autosquash
You 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

49. CUSTOMARY
WARNING!
rebase rewrites history!
Treat this power with great care.
Only rewrite history of local branches or…

50. Prevent tampering

51. Always a balancing act
Security DevSpeed

52. PREVENT TAMPERING
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:

53. 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

54. Reject force push,Luke

55. Reject force push,Luke

56. PREVENT TAMPERING
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

57. PREVENT TAMPERING
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

58. Signing release tags is often
all you need

59. PREVENT TAMPERING
Aside on GPG
The GNU Privacy Guard
GnuPG allows to encrypt and sign your data and
communication, features a versatile key management system.

60. PREVENT TAMPERING
Harden up by signing things
Sample gpg commands to get you started:
gpg --gen-key
Generate your GPG keys
gpg -k
List your keys
gpg -a --export <keyid>
Export your key

61. PREVENT TAMPERING
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

62. PREVENT TAMPERING
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

63. PREVENT TAMPERING
Import other public keys
git cat-file -p tims-key | gpg --import
Import a GPG key from a tag

64. PREVENT TAMPERING
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

65. and Project Dependencies

66. How do you handle
project dependencies
with ?

67. Splitting up a project
is painful, for so many
reasons

68. Use a build/dependency
tool instead of

69. GIT AND PROJECT DEPENDENCIES
I’ll give you an incomplete list of examples!
Java
Nodejs
Javascript
Python Pip easy-install
Ruby

70. GIT AND PROJECT DEPENDENCIES
I’ll give you an incomplete list of examples! (2)
C#
C++ c-make
Objective C
PHP
Go godep

71. Another possibility:
use git submodule

72. Another possibility:
use git subtree

73. Use other build
and cross-stack
dependency tools

74. GIT AND PROJECT DEPENDENCIES
•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:

75. PRO ALIASES & PROMPT
Review these ideas online
http://bit.do/git-deps

76. CONFLICT RESOLUTION TIPS
HIDING STUFF
Today we covered:
POLISH YOUR CODE
PREVENT TAMPERING
PROJECT DEPENDENCIES
PRO ALIASES & PROMPT

77. NICOLA PAOLUCCI • DEVELOPER INSTIGATOR • ATLASSIAN • @DURDN
Thank you!
Mechelen - 26th November
@durdn