Git and Github workshop

Workshop
Git and Github for beginners
(and something for advanced too)
Otto Kekäläinen
Startup.bg 6.11.2015
Sofia,Bulagaria

@ottokekalainen
●
15+ years in open source
●
technology & business & advocacy
●
development with git since 2010

The MariaDB Foundation
Continuity and open collaboration
●
MariaDB.org sponsors include MariaDB.com,Booking.com,
Automattic,Odin/Parallels,Visma...
●
Employs 6 persons,including ”Monty”Widenius,the creator of
MySQL/MariaDB
●
Single contact point for collaboration and contributions
●
The Foundation makes sure all pull requests and patches are
reviewed
●
All development work done with git at github.com/mariadb

Outline
1.The story of Git
2.Basic commands
3.Doing it with Github
4.Git internals
5.Advanced commands
6.Git everywhere?

Git / t/ɡɪ
”A silly,incompetent,stupid,
annoying or childish person.”
http://en.wiktionary.org/wiki/git

"I'm an egotistical bastard,so I
name all my projects after myself.
First Linux,now Git”
Linus Torvalds,PC World.2012-07-14

Linus needed a new source code revision manager for
Linux,and none of the available options in 2005 where
good enough,so he wrote his own in.
Kernel 2.6.12 was the first release managed by Git and
version 1.0 of Git was released in December 2005.

Design goals of Git:
●
distributed revision management
●
protection against corruption,
both accidental and hostile
●
speed

Git popularity according to OpenHub.net

Git popularity according to Google Trends
git
svn

...but adoption would be faster if it was
not so difficult to use.
Originally Linus did not intend end users to use Git
directly,instead he tried to delegate to somebody
else the task of making the actual command line
interface. We are still waiting for it...
Luckily Git has been simplified and documentation
has improved over time,but some Git commands
still refer to Git internals that are difficult to grasp.
E.g. git-push: Update remote refs along with
associated objects.

Git might feel difficult at first,
but once you learn it, you never
want to go back to anything less
flexible and powerful.

Install on Linux:
apt-get install git git-gui
Install on Mac/Windows:
git-scm.com/downloads

First obstacle: same terms with different meanings

git config --global user.name "John Doe"
git config --global user.email johndoe@example.com
Define the author of commits

git init
git add example.txt
git commit -am “First commit”
# edit files
git commit -am “Second commit”
Start a new repository

git pull
# edit files
git commit -am “Implemented X”
git push
git log
git show
Typical workflow

Visit http://try.github.com/
After making your first repository,set up SSH key
for convenient authentication:
https://help.github.com/articles/generating-ssh-keys
Note: Github is not the only Git hosting site,
Gitlab and Bitbucket are popular too.

Exercise:
-go to https://github.com/ottok/git-training and fork it
-look at the fork under your own Github account and
clone it to your laptop
-edit names.txt and add yours
-push changes back to Github
-in Github,do a merge request back to me

git clone git://github.com/<yourname>/git-training.git
# edit names.txt
git commit -am “Added my name”
git push
# Open pull request on Github

The best part of Github is pull
requests,and how they enable
frictionless collaboration among
millions of developers

Folder /.git contains everything,
your / is just the working copy.

Folder /.git contains everything,
your / is just the working copy.
When you commit a 2 MB file /example.png,
your / will grow to 4 MB...

When you add a file,
it goes to the staging area.
The file does not go into the
actual history tree until the stage
is committed.

Commands push and pull and many other commands
are shortcuts that act with both
your local repository and the remote repositories.

Image credits Steve Bennet (http://steveko.wordpress.com/2012/02/24/10-things-i-hate-about-git/)

Git tracks content,not files!
Git history is immutable as each commit ID is the SHA-1 of
the commit data and metadata (including the commit ID of
parents).Changing any commit in the history will change the
SHA-1 commit IDs of every following commit in the chain.
If you need to change something in the history,you have to
rebase and make a new history.

Git commit IDs and rebase
Original 'git log --oneline':
1bf7024 MDEV-8991: bind-address appears twice in default my.cnf
b2205c5 MDEV-9011: Redo log encryption does not work
cf9e6b2 Fix test failures seen on buildbot.
923827e MDEV-7949: Item_field::used_tables() takes 0.29% in OLTP RO
239e0c5 MDEV-8551 compilation fails with 10.1.6
After 'git rebase -i HEAD^^^':
34350b9 MDEV-8991: bind-address appears twice in default my.cnf
f5f2dd9 MDEV-9011: Redo log encryption does not work
531e1ac Fixed all bugs
923827e MDEV-7949: Item_field::used_tables() takes 0.29% in OLTP RO
239e0c5 MDEV-8551 compilation fails with 10.1.6

Branches and tags
Basically just labels that point to certain commit IDs.
Each commit ID point to its parent,thus forms a chain.

How to write a good commit message
●
Your attitude towards commit messages should be the same as for code: it is
written once,but read thousands of times.
●
Don't explain how was done,that is visible in the diff anyway.Explain what the
intention was and why it was made.
●
Use imperative form “Fix typo”(instead of “Fixed typo”)
●
Keep subject line short and sweet,under 72 chars.Body can be verbose.
●
Use proper English.Capital letters.Reference issue identifiers is possible.
●
Looking for a good example? How about one by Linus himself?
https://github.com/torvalds/linux/commit/fc90888

Sorry,but default commands not very friendly,so get
yourself good cheat cheets and write up your common
commands once you've figured them out..
Image credits Steve Bennet (http://steveko.wordpress.com/2012/02/24/10-things-i-hate-about-git/)

Example of how fast-forward works 1/2
●
Branch“feature-branch-example”forked from master branch
“10.1”and has 3 commits

Example of how fast-forward works 2/2
●
Normal merge defaults to fast-forward in this case
●
●
●
Result of no fast-forward (git merge --no-ff)

Want to avoid “ugly”merge commits?
●
git config pull.ff=only
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git config alias.ff=merge --ff-only
●
Run 'git rebase master'to rebase you work on the master
branch before pushing or making pull request
●
Run 'git merge'on when importing changes from remote
head only if you really want to merge

Want to put a simple shared repository on any SSH
capable server? Create a bare .git with no working files:
git init --bare
Want to have notifications when somebody commits?
Put a shell script at .git/hooks/post-receive

Would you like to store all your files in Git?
Git-annex
Diff of binary files?
Add in .git/config
[diff"odf"]
textconv=odt2txt
See also: http://www-verimag.imag.fr/~moy/opendocument/

Bug tracker as part of project?
http://bugseverywhere.org/
Bug tracker and wiki contents in Git?
trac+git
Clone wiki from Github with
git clone https://github.com/YOUR_USERNAME/YOUR_REPOSITORY.wiki.git

Publish to the web with one commit?
self-hosted Jekyll or
on Github https://pages.github.com/
Open source alternative to Dropbox based on Git?
http://sparkleshare.org/

Would you like others to
contribute to your software?
Provide easy forking (git clone),
easy way to develop new feature (git branch),
and an easy way to send them back (merge request).

Will Git credits replace developers CV's?

Is there anything we can't store and track in Git?

Git and Github workshop

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