CSC/ECE 517 Fall 2010/ch3 3e br

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Introduction

Version Control Systems are typically used in a software facility(s), and employed for the primary purposes of collaborative work. While working on a project with common resources (files, folders, information etc.), it becomes essential to put a definite order on the sanctity of the data if the resources are editable.

For example, if there are 10 people working on a project, and 3 people are working on the same file. It becomes important on how they can add/modify data such that all are neither locked out waiting for a lock put by anyone, nor there is any inconsistency in the data. Also, at any point in the life-cycle of the software, the developers might feel the need to go back to an earlier state of the file. Version Control Systems allow to go back to any previous version of a file, as each version is stored in the central repository and is given a label.

Version control systems typically let us create versions of the resources, where each developer can work on a different version, therefore providing the flexibility. There are a whole bunch of features provided by the new Version Control Systems. We shall look at the evolution and history of the same in the subsequent sections.

Taxonomy of Version Control

Branch : When the development team needs to work on two distinct copies of a project, a branch is created. [4] The branch is a replica of the existing code at the time of its creation. On creation of the branch, changes made to a branch are confined to it and are not visible in any other branch.

Repository: Repository is the data store where all the versions of all the files in the project are stored. A repository may be centralized or distributed.

Check-Out: Creating a working copy of the files in the repository on a local machine is called Check-out. Every user who checks out a file has a working copy of the file on his computer. Changes made to the working copy are not visible to the team members

Check-In: Putting back the edited files to the repository for use by everybody is called Check-In

Merge: Merging is the process of combining different working copies of the file into the repository.[3] Each developer is allowed to work on their independent working copies, and everyone’s changes to a single file are combined by merging

Label: A label is an identifier given to a branch when created. Also known as Tag

Trunk: The highest location of the repository is called Trunk.


History of Open Source Version Control Systems

Source Code Control System (SCCS)

The exact time in history when and how the version systems came about into existence is unclear. However, we can estimate roughly that the version control system can be rooted to the Source Code Control System (SCCS) [3],[6]. It was developed by the Bell Labs in 1972. It is no longer prevalent, but the file format is still internally used today by other softwares like BitKeeper and Sablime[6]

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