How to work on git (my personal experience)

You can work on two type of repository on github 1 - those which you have push permissions 2 - thos which you don't have push permissions and you need a "pull request" to add your developments

While the develop on the repository of type 1 can be faster and simpler, it requires more attention when commit and push. The type 2 is more safe, but requires more steps.

Let's start from type 2, that covers the h2gglobe case.

First of all, start with copying the entire repository from the central place to your personal github area. This step is called "fork" and should be done only once.

Go on the github page of the repository you want to copy: for example https://github.com/CMSROMA/gitTest On the upper right part of the page there is a button "fork". Select @yourusername as destitation in order to fork into your personal github area.

Now you have the perfect copy of the central repository.

== The second step is to make a clone of the repository on your local machine (can be lxplus or your own personal computer). I do: git clone [email protected]:shervin86/gitTest.git

you should put your github username instead of shervin86.

== Now you have a working copy on your CMSSW relase probably. Few concepts:

• your are working on a branch that is called "master" my advice is to never commit directly on this branch
• you should create a new branch with a reasonable name (for example "newSelection", please don't use "pippo")
• move on that branch
• start to right the code
• commit the changes frequently with meaningful messages
• if you have finished (only if you have finished!), move to the "master" branch
• merge the "newSelection" branch with the master
• then push the updates to your personal copy on github
• if it's fine and you finished all the changes, make a pull request to merge your work with the central repository

Now, an example, still conceptual without commands:

• I forked the TopHiggsAnalysis from CMSROMA into my github
• I cloned my version of TopHiggsAnalysis, I have it on my laptop
• I have to update 3 things: 1) few cuts in the analysis, 2) the PU reweight for the run dependent MC, 3) fix the macro for the plots
• I create 3 branches: newSelection, puReweight, plotMacro
• I'm on the master and I move to the plotMacro to start to work on that
• I do some changes and I commit them
• I'm tired and I want to move to the puReweight stuff also if I've not finished with the plotMacro
• I change the branch (I have to be sure to have committed all the changes for plotMacro before)
• I do the changes and I commit many times
• Now the work for puReweight is finished, for plotMacro is ongoing and for newSelection is not yet started
• I move to the "master" branch, I merge the puReweight and I push to the github repository
• I don't need the puReweight branch anymore and I delete it
• now on github only the master has been updated
• I can push the new branches newSelection and plotMacro to the repository in order to have them saved also on the server
• another day I can switch to one of the remaining branches to continue to work, then I will merge with the master once finished and I push the master.

• Fork the gitTest into your github by clicking on the fork button

• clone it into your computer or area (I do it using the CMSROMA/gitTest link, you should use the one of your github area) git clone [email protected]:CMSROMA/gitTest.git

• create the branches indicated in the example before git branch newSelection git branch puReweight git branch plotMacro

• I move to the plotMacro branch git checkout plotMacro

• create a new file: shervin.C touch shervin.C

• add this file to the list of tracked file: the files that are under revision git add shervin.C

• add 2 new files in a new directory mkdir macro/; touch file1.C; touch file2.C

• add all files in the new directory (you cannot add empty directory!) git add macro

• now commit every change git commit -m "log message" -a

• now modify file2.C and file1.C

• commit only file2.C git add macro/file2.C git commit -m "changin only file2.C"

• now change also shervin.C, add a new file3.C and commit all changed files git commit -m "only tracked files are committed!" -a

• if I finished with all the development with this branch I can merge it with the master: git checkout master git merge plotMacro

• now I can update my github repository pushing the master branch to the origin (the repository from which I've done the clone) git push origin master

• redo all the commits and changes with another branch: newSelection

• move to the newSelection branch git checkout newSelection

• create files and directories, add them to the repository and commit

• now we have not finished and you want to keep the branch tracked in the repository on github git push origin newSelection

• this have created a newSelection branch on github with your commits

• Only when you have finished, you are ready to propose your changes to the main repository

  • You need to have merged everything you want to propose to the master

  git checkout master

  git merge newSelection

  git push origin master

  • make pull request on github selecting the master on your github area and the master of the gitTest (or the repository you forked)

It's fine to work in more than one on the same github repository, but I advice to

• start from the same point
• use the master or a new branch to coordinate
• make one branch per person and merge frequenty solving conflicts