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Software Revision Control

Software Revision Control. CSE301 Harry Erwin, PhD. Sources. Mostly Wikipedia and various web articles. Revision Control. Software Configuration Management Management of changes to documents, programmes , and files. The following are available on my Mac OS X web server: CVS

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Software Revision Control

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  1. Software Revision Control CSE301 Harry Erwin, PhD

  2. Sources • Mostly Wikipedia and various web articles

  3. Revision Control • Software Configuration Management • Management of changes to documents, programmes, and files. • The following are available on my Mac OS X web server: • CVS • SYN (Subversion) • Git

  4. Approaches • Centralised management • Decentralised management

  5. Terminology • Baseline—an approved revision • Branch or fork—splits a set of files under version control • Change, diff, or delta—a specific modification • Checkout—creates a local working copy • Commit or checkin—writing a set of changes back into a repository • Conflict—two incompatible changes • Export—checkout without the version-control metadata • Import—copying files into the repository for the first time • Merge—bringing two sets of changes into compatibility • Repository—the home of the files • Revision—also known as version of the repository • Working copy—local copy of files from the repository

  6. Centralised Source Management • Two Alternative Approaches • Atomic operations—use a gray code approach to ensure the repository is left in a consistent state • File locking—locks files at checkout so only one user may make changes • Version merging—delicate, requires some means of identifying inconsistencies • Baselines, labels, and tags—used to describe a version of the files in the repository.

  7. Distributed Source Management • Peer-to-peer approach. • Each developer has a bona-fide repository. • Changes coordinated by sharing patches. • Operations are fast, because there is no central server. • Each working copy is a remote backup.

  8. CVS • Maintained but not developed. • Centralised • Atomic merge • Free

  9. SVN • Apache Subversion • Actively developed • Centralised • Supports merge and lock • Free

  10. Git • Actively developed • Distributed • Provides various 3-way merge strategies (two or more documents and one or more parent documents) • Free

  11. CVS • Originally a collection of shell scripts (1986) • Client-server architecture • No atomic commit 8( • Only the latest version of a file can be changed. Developers have to manually update that version if it has changed since they started development on the file. • Maintaining the local copy is mostly automatic. User intervention for edit conflicts. • Final version May 2008.

  12. Anonymous CVS • Users who want to have the latest version but are not actively developing, can checkout with a standard password. • Checkin requires a user ID and password.

  13. SVN • Mostly compatible successor to CVS • Sponsored by CollabNet • Top-level Apache project on Feb 17, 2010 • Commits are atomic operations • More flexible than CVS • Access to repository: • file:///path • WebDAV/Delta-V (mod_dav_svn) • svn://host/path (port 3690) • svn+ssh://host/path

  14. Git • Fast! • Distributed • Non-linear development • Initially by Linus Torvalds • Every Git working directory is a repository • Invented as an alternative to BitKeeper. • Inverts CVS (like UNIX inverts Multics) • Safeguards against corruption. • Uses 3-way merge in various forms.

  15. Using Them • Go here: sshyouraccount@crowan-scat.sunderland.ac.uk • Use cvs, svn, or git by typing in the command. • Demo at this point…

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