ROOT Analyzer/Git

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It has been proposed that Hall C use the Git version control system to manage development of the Hall C 12 Gev analysis software. To start working with git, a public repository of a bare skeleton of a Hall C analyzer based on the Hall A PODD analyzer has been created.

Some general information on how to work with git can be found on the Git Howto page, and at [#Git References].

One can view the git repository of hcana on the web.

Instructions for getting write access to our git server are outlined here: hallcgit.jlab.org. Read-only access does not require a special account.

Setting up Git

You should have git, with at least version 1.5.3 installed on your computer. Most linux systems will have git installed.

  • NOTE: git 1.7.x (or newer) is much, much better. We should have this rolled out on most machines at JLab and it is typically the default on personal installations. If you find an older version on a JLab-controlled machine you are advised to request an upgrade by submitting a JLab CCPR.

Personalize git on your machine with

 git config --global user.name "Firstname Lastname"
 git config --global user.email "your_email@youremail.com"

By default, git pops up the vi editor for the user write comments when making commits. If you prefer emacs, do

 git config --global core.editor "emacs"


Retrieving the Hall C analyzer skeleton with git

The Hall C code is hosted on hallcgit.jlab.org. There is also a read-only mirror on github.com at [1]. To retrieve the code, follow one of the two sections below:

Read-only access

To retrive the Hall C code with git, do

 git clone git://github.com/sawjlab/hcana.git

This should work from machines on- and off-site now.

Read/write access

The read-write git archive is hosted on hallcgit.jlab.org. Access to this server is by request only. Please send your public ssh key (id_dsa.pub) to Steve Wood who will install it on the server. (See hallcgit.jlab.org for more information on using this server.) Once that is done, do

 git clone git@hallcgit.jlab.org:hcana.git


Either of these two methodes will create a directory "hcana" containing a checked-out working copy of the "develop" branch and containing the revision history of the code.

The hcana project includes a git "submodule" containing the source code for the Hall A analyzer. The Hall A code is not automatically downloaded with the "git clone" command. Before proceeding, do

 cd hcana
 git submodule init
 git submodule update

If your version of git is too old, (as it is on many jlab machines including ifarm*), this last command may give an error. In that case, edit the file ".git/config", find [submodule "podd"] section and edit it to look like:

 [submodule "podd"]
          url = git@hallcgit.jlab.org:podd.git

(i.e., remove the extraneous "hcana.git/") and repeat the "git submodule update" command.


After you have setup this copy of the code, do the command

 git pull

each time before starting to use or edit the code to make sure that you have updated your copy with the latest changes.

See Analyzer/Compiling and Analyzer/Running to try out the code.

Using Git to develop the analyzer

We need to have a workflow methodology for developing the Hall C analyzer. "Understanding the Git Workflow" and "Our Simple Git Workflow" have some discussion of straight forward workflows.

Basically if you want to develop the analyzer, clone the git archive as described above. Then create a private branch for yourself with

 git checkout -b myprivatebranch

Then work on the code do git commit -a frequently. Don't worry about committing changes frequently. You will have the opportunity to clean up the revision history before pushing your changes to the public repository.

There are a variety of ways to share your work. If someone you want to share it with is on the same machine (and your files are readable), he can clone or pull from your archive. If your working directory is available on the web, then anyone can clone or pull from it. To put your changes in the public git repository, contact one of the code maintainers.

Branches

The git repository may contain several branches in addition to the default "develop" branch. These branches may be for different experiments, or for work in progress that a developer wants to share. To see what branches exist, type

 git pull origin    #Updates the local repo from the public repo
 git branch -a

from the directory you cloned the project into. For example, at the moment, there is a branch "simon-shower" which contains code being developed for the shower counters. This branch will be listed as "remotes/origin/simon-shower". To check this branch out, type

 git checkout simon-shower

The master branch is reserved for major releases.

Publishing Changes

It is important that any code development be made public early and often. If you have previously retrieved the analyzer from github, you need to change to the hallc git server to be able to push code. To setup the ability pushlish your work to the public repository, edit the file "hcana/.git/config". Find the sectioon [remote "origin"]. Then replace "url" line after it with

       url = git@hallcgit.jlab.org:hcana.git

Github will have to be told to allow access from your account. To do this, contact Steve Wood.

To publish changes, make sure you are doing your work in a branch other than develop. When you are ready to post it, do

git push origin branchname

Then let Steve Wood know and he will merge your code into the develop branch.

Git References

Brad's Hall C wiki Git_Howto page

Git Magic: An online book about using Git.

The Git Community Book: The official book introducing Git.

Understanding the Git Workflow

Our Simple Git Workflow

Git flow used by GitHub

We will try to follow the branching model described in: A successful Git branching model