Using  Git  101  

Sebas/en  Goasguen    @sebgoa  

 

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      

                               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      

                         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  

 

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/pull  to  each  other    

   

hOp://i.stack.imgur.com/9IW5z.png      

     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!

                       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  

     

   Create  a  Gist  

   

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

     

                           See  your  first  version    in  the  UI  

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        

                           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!

               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).  

                       See  the  revisions  

                               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  

       

                                       Clone  CloudStack  

     

     

git clone https://git-wip-us.apache.org/repos/asf/incubator-cloudstack.git!

•  Which  branch  are  you  on  ?  

$ git branch!* master!

     

                           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          

                           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>!

                     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  

                       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.  

                         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.!

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          

                 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  

         

                           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    

       

                         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  

                         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!

                           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/    

       

         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