Information Systems Concepts Version Control

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Information Systems ConceptsVersion Control

• Dell Zhang
• Birkbeck, University of London
• Spring 2009

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Version Control

• A Version Control System (VCS) lets you track
  your files over time
• Also known as
• Revision Control
• Source Control
• (Source) Code Management

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Version Control

• Why do you care?
• Have you ever saved a file, and then wanted to
  revert the changes you made? Have you ever wished
  you could see what a file looked like some time
  ago?
• Do you work in a team? Has it ever happened that
  you were working on a file, and someone else was
  working on the same file at the same time? Did
  you lose your changes to that file because of
  that?
• Have you ever found a bug in your project and
  wanted to know when (and how) that bug got into
  your files?

--- Version Control with Subversion.
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Version Control

• You have probably cooked up your own VCS. Got any
  files like these?
• report-old.pdf
• logo_v3.png
• logo_v4.png
• ResumeOct2006.doc
• ResumeMar2007.doc

Thats why we use Save As.
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Version Control

• A Poor Mans VCS
• Make a single backup copy (Document.old.txt).
• If were clever, we add a version number or date
  Document_V1.txt, DocumentMarch2007.txt
• We may even use a shared folder so other people
  can see and edit files without sending them over
  email. Hopefully they re-label the file after
  they save it.
• Does this work for a large-scale development
  project (such as Microsoft Windows)?
• Not a chance.

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Version Control

• Central (Client/Server) Model
• CVS
• Subversion (SVN)
• Distributed Model
• Mercurial
• Git

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A Typical Central (Client/Server) Version Control
System
--- Version Control with Subversion.
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The Problem to Avoid
--- Version Control with Subversion.
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The Lock-Modify-Unlock Solution
--- Version Control with Subversion.
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The Copy-Modify-Merge Solution
--- Version Control with Subversion.
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The Copy-Modify-Merge Solution
--- Version Control with Subversion.
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--- A Visual Guide to Version Control.
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--- A Visual Guide to Version Control.
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Most VCS store diffs rather than full copies of
the file.
Whats the diff from r1 to r4?
--- A Visual Guide to Version Control.
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Branches of Development
--- Version Control with Subversion.
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The Branching of One Files History
--- Version Control with Subversion.
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--- A Visual Guide to Version Control.
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--- A Visual Guide to Version Control.
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--- A Visual Guide to Version Control.
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--- A Visual Guide to Version Control.
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A real-life example
Reverse Integration (RI) and Forward Integration
(FI)
--- A Visual Guide to Version Control.
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