GIT Primer

GIT is a distributed version control system.

• Comparable idea to SVN: preserve all revisions of source code
• Cowever: not a client-server architecture like SVN with a repository server and client-side working copies

Core concepts:

• Everyone has a full repository with all branches and revisions (cloned from a remote server)
  • Checkout -> clone
• Branches are fundamental to development
  • Well supported (especially merging)
• Support for compound repositories
  • Contents of one repository can be made available in the context of another one as a submodule
  • Comparable to svn:externals

Getting Source Code: Cloning a Repository

For a simple repository:

git clone https://code.cor-lab.org/git/rsc.git rsc

For a repository containing submodules:

git clone --recursive https://code.cor-lab.org/git/rsb.git rsb

Getting the Correct Software Version in a Repository

A cloned repository contains all revisions of its software with all branches and the user needs to select a branch he wants to have available at the moment. Therefore, he needs to checkout the respective branch.

Listing available branches:

git branch -a

For a simple repository (e.g. rsc):

git checkout 0.7 # 0.7 being the branch name

For a repository containing submodules (e.g. rsb, rst) this can be done recursively:

git submodule foreach git checkout 0.7
git submodule foreach git pull --rebase

The additional pull step (see below) is necessary as the repository containing the submodules points to a specific revision and not the latest one in each branch. Therefore, we need to get the most recent changes in the branch.

General Tasks with GIT

• Getting the latest changes from the server

  git pull --rebase
  

  Note

  By using --rebase local commits (not yet pushed to the remote server) are applied again after fetching all revisions from the remote repository. Otherwise and intermediate branch would be created and merged back directly.

• Commiting changes

  git add {files to commit}
  git commit
  

  Warning

  Committing in GIT is not comparable to committing in SVN. Eventhough your commit has created a new revision, this revision is only available in your local clone of the repository. You still need to push it back to the server. So do not forget the next step!

• Pushing local changes back to the remote repository

  git push