An introduction to version control using git, github and the Apache CloudStack git repository. Git is a distributed version control where developers can mantain a working local copy, make local changes and push to a central repository to share their code with other developers. Git has replaced SVN and CVS has the version control system of choice, especially with the adoption of github by the OSS community. In this talk we show the basics of version control, we use gist from github to put simple scripts under version control and submit patches to it. We then show how to clone the cloudstack repository, explore the various feature and release branches. We then show how to create a patch and submit it to the Apache Software Foundation review board so that a committer of the CloudStack community can pick it up and apply it to the source tree. This is the perfect talk to discover git and submit your first patch to CloudStack.

1. Using
Git
101
Sebas/en
Goasguen
@sebgoa

2. Outline
• Intro
to
version
control
and
Git
• Crea/ng
your
first
git
repo
using
Gist
• Cloning
the
CloudStack
repo
• Managing
branches
• Making
your
first
commit
• Applying
a
patch
NB:
Check
the
footnotes
for
addi/onal
informa/on

3.
Version
Control
• Revision
control
(a.k.a
version
control)
is
the
management
of
modifica/ons
of
digital
informa/on.
• In
the
context
of
soMware
engineering
it
represents
the
management
of
the
mul-ple
versions
of
a
so3ware
as
it
evolves.
• In
other
terms
it
tracks
changes
in
the
source
code.
hOp://en.wikipedia.org/wiki/Revision_control

4.
Version
Control
Systems
• Historically:
– Centralized
systems
used
– Concurrent
Version
System
(CVS)
– Subversion
(SVN)
• Currently:
– Distributed
version
control
– Git
(2005)
– Mercurial/hg
hOp://cvs.nongnu.org
hOp://subversion.apache.org
hOp://git-­‐scm.com
hOp://mercurial.selenic.com

5. Workflow
• Developers
clone
a
central
repository
• Local
repository
is
a
working
copy
• Updates
are
made
locally
(fast)
• When
done,
changes
are
pushed
back
to
master
• Developers
could
push/
hOp://i.stack.imgur.com/9IW5z.png
pull
to
each
other

6.
Ge]ng
Git
• Apache
CloudStack
(ACS)
uses
Git
as
distributed
version
control
system
• Install
git
on
your
machine.
Depending
on
your
OS
and
package
manager:
! !#yum install git-core!
! !#apt-get install git!
! !#port install git-core!

7.
Tour
GitHub
• Check
the
publicly
accessible
repositories
• Create
an
account
Exercise:
• Check
Gist
• Put
a
document
under
revision
control
hOps://github.com/repositories
hOps://gist.github.com

8.
Create
a
Gist
Copy/Paste
code
or
text
in
the
main
window,
add
a
decrip/on.
hOps://gist.github.com

9.
See
your
first
version
in
the
UI

10. Clone
gist
$git clone https://gist.github.com/5027212.git!
Cloning into '5027212'...!
remote: Counting objects: 3, done.!
remote: Compressing objects: 100% (2/2), done.!
remote: Total 3 (delta 0), reused 0 (delta 0)!
Unpacking objects: 100% (3/3), done.!
$ cd 5027212/!
$ ls!
crawler.py!
NB:
Here
crawler.py
is
just
an
example,
you
will
have
a
different
filename

11.
Modify
and
Commit
your
Gist
$ vi crawler.py !
$ git add crawler.py !
$ git commit -m "This is a gist test"!
• [master 578d363] This is a gist test!
• 1 file changed, 2 insertions(+)!
$ git push!
Username for 'https://gist.github.com': runseb!
Password for 'https://runseb@gist.github.com': !
Counting objects: 5, done.!
Delta compression using up to 4 threads.!
Compressing objects: 100% (2/2), done.!
Writing objects: 100% (3/3), 312 bytes, done.!
Total 3 (delta 1), reused 0 (delta 0)!
To https://gist.github.com/5027212.git!
04d6d71..578d363 master -> master!

12.
Explana/ons
• We
opened
the
file
and
made
some
changes
• We
made
sure
the
changes
were
being
tracked
(git
add).
• We
commi:ed
the
changes
to
our
local
repository
(git
commit).
• To
share
these
changes
with
others
we
pushed
them
to
the
remote
repository
(git
push).

13.
See
the
revisions

14.
Browsing
CloudStack
Explore
the
latest
commits,
view
the
diffs,
browse
the
various
branches
hOps://git-­‐wip-­‐us.apache.org/repos/asf?p=incubator-­‐cloudstack.git

15.
Clone
CloudStack
git clone https://git-wip-us.apache.org/repos/asf/
incubator-cloudstack.git!
• Which
branch
are
you
on
?
$ git branch!
* master!

16.
What
is
a
branch
?
• A
branch
keeps
track
of
a
history
of
code
changes.
• Mul/ple
branches
keep
track
of
diverging
histories
of
code
changes.
• You
can
switch
between
branches
to
work
on
code
changes
without
impac/ng
another
branch
• You
can
merge
branches
to
unify
histories
hOp://git-­‐scm.com/book/ch3-­‐1.html

17.
Iden/fy
an
ACS
branch
$ git remote show origin!
* remote origin!
Fetch URL: https://git-wip-us.apache.org/repos/
asf/incubator-cloudstack.git!
Push URL: https://git-wip-us.apache.org/repos/
asf/incubator-cloudstack.git!
HEAD branch: master!
Remote branches:!
4.0 tracked!
4.1 tracked!
!
<snip>!

18.
Branching
• Releases
are
kept
in
their
own
branch
(e.g
4.0,
4.1)
• Features
are
being
developed
on
their
own
branch
(e.g
ipv6,
events-­‐framework)
• Default
branch
is
master
• You
can
checkout
a
remote
branch
• You
can
create
a
local
branch

19.
Checkout
4.0
$ git checkout 4.0!
Branch 4.0 set up to track remote branch 4.0 from
origin.!
Switched to a new branch ’4.0’!
$ git branch!
* 4.0!
master!
!
• You
now
have
a
4.0
local
branch
which
tracks
the
4.0
remote
branch.
• Changes
in
your
local
branch
is
not
propagated
to
the
remote
un/l
you
push.

20.
Syncing
with
Others
• Other
developers
will
push
changes
to
the
remote
repository.
• To
make
sure
you
stay
in-­‐sync
with
the
remote
you
need
to
pull
changes
to
your
local
branch
• A
pull
will
try
to
merge
changes
in
the
remote
with
your
local
branch.
It
may
result
in
conflicts.!
$ git
pull
!
Already up-to-date.
!

21. Branching
• Get
familiar
with
branching
on
your
local
repository
• Create
branches,
switch
between
them
and
delete
them
$ git checkout –b foobar!
$ git branch!
$ git checkout master!
$ git branch!
$ git branch –D foobar!
hOp://git-­‐scm.com/book/ch3-­‐1.html

22.
Configure
git
vi ~/.gitconfig!
git config –global user.name “your name”!
git config –global user.email you@email.com!
!
!
• There
are
a
lot
more
configura/on
possible
hOp://incubator.apache.org/cloudstack/develop/non-­‐contributors.html
hOp://git-­‐scm.com/book/en/Git-­‐Basics-­‐Tips-­‐and-­‐Tricks

23.
Your
first
ACS
Patch
• AMer
cloning
the
ACS
repository
• Create
a
local
branch
(e.g
mybranch)
• Edit
the
files
you
want
to
modify.
(e.g
Add
some
documenta/on,
fix
a
bug
from
JIRA)
• Stage
your
changes
and
check
that
you
did
not
forget
any
files.
• Commit
to
the
local
branch.
• Create
a
patch.
hOps://issues.apache.org/jira/browse/CLOUDSTACK
hOp://incubator.apache.org/cloudstack/develop/non-­‐contributors.html

24.
First
Patch
$ git checkout –b mybranch!
!
• Make
the
changes
you
want
$ git add <file you changed>!
$ git status –s!
$ git commit –m “Comment your changes”!
$ git format-patch master –stdout > ~/
myfirstpatch.patch!
!
!
• Look
at
the
content
of
the
patch

25.
Verify
the
Patch
• It
is
a
good
idea
to
check
that
your
patch
can
be
applied
cleanly
• Create
a
new
branch
star/ng
from
master,
apply
your
patch,
if
successful
submit
to
review
board
$ git checkout master!
$ git checkout –b testbranch!
$ git apply --check ~/myfirstpatch.patch!
$ git apply ~/myfirstpatch.patch!

26.
Submit
patch
• If
you
don’t
have
write
access
to
the
remote
repository,
you
need
a
mechanism
to
send
your
patch
upstream.
• In
ACS
we
use
Review
Board.
Create
an
account
and
enter
a
review
request.
hOp://incubator.apache.org/cloudstack/develop/non-­‐contributors.html
hOps://reviews.apache.org/dashboard/

27.
Conclusions
• Learn
and
Use
version
control
• Simple
cases
are
well…simple
J
• Git
is
used
heavily,
create
a
personal
github
account
• Apache
CloudStack
uses
Git
• Prepare
patches
and
send
them
to
us
• Become
an
Apache
Commi:er