Version Control...
Version control is a system that records changes to a file or set of files over time so that you can:
- Undo mistakes - keeps track of all your changes in time.
- Work concurrently with a team of people without affecting each other's code.
- Work concurrently on different versions of a project - develop and test new features without affecting a working project.
Repositories & Working Copies...
- A version control uses a repository, which is a database of all project changes, and a working copy (checkout), which is a personal copy of all the files in the project.
- Changes are made to the copy, without affecting the teammates.
- When done, changes are committed to the repository.
Workflow...
- Update your copy from the server.
- Make your changes, & make sure they work properly.
- Commit your changes to the server.
Version Control Types...
Centralized Version Control Systems...
System consisting of a single server that contains all the versioned files, and a number of clients that check out files from that central place. For many years, this has been the standard for version control.
Advantages
- One person can control it.
- It is easier to administer a CVCS than to deal with local databases on every client.
- A master copy of the code is kept centrally.
- To a certain degree, everyone knows what others are doing on the project.
Disadvantages
- What will happen if the server goes down?
- No one can collaborate nor save versioned changes.
- What if the hard disk with the central database becomes corrupted?
- If proper backups haven’t been kept, you lose everything.
Distributed Version Control Systems...
In a DVCS, clients fully mirror the the repository. If any server dies, any of the client repositories can be copied back to the server to restore it.
Version Control Concepts...
Repository...
- Location were all versioned products are stored.
- Can be a structured directory on a server with each versioned file stored separately.
- Can be a database containing entries for the various files in a project.
- Can be a complex distributed system that redundantly stores the versioned project in many places.
Working Directory...
- Developers do not work on the files in the repository, but on a copy called as working directory accessible locally on their development machine.
- Once done with the work, the developer commits the changes back into the repository where other developers now have access to them.
Revisions...
- The system does not only store the most recent snapshot of a project many snapshots are stored over time.
- A committed change (snapshot) to a repository is referred to as a revision.
Logs...
- Enable you to keep track of what has been changed, when and why.
Tagging...
- Marking revisions so they can be referred back to at a later time.
- Usually you mark revisions at milestones to make it easier to go back and search out the cause of a newly discovered bug.
Branching...
- Allows creating additional paths of development in a repository (for example, implementing and testing a feature of a project).
- Each branch is worked on independently including commits only affecting the branch they are made on.
- Branches can be merged if needed.
Merging...
- Version control checks for collisions on commits and attempts to automatically merge the file. If not possible, provides the developer with ability to merge changes manually.