Download - CS 501 : An Introduction to SCM & GForge An Introduction to SCM & GForge Lin Guo [email protected]
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Roadmap
What is SCM Why do we need SCM Interesting SCM features SCM tools GForge Conclusion
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What is SCM
Source Control Management Maintain a repository of source files Track all changes Control changes
Software Configuration Management More than source control Manage source repositories
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Why we need SCM
Source Control Sharing: supports concurrent development Versioning: provide version number and dates Change tracking: find details of a change Archival: reproduce any file from any point Documentation, drawing, etc.
Configuration Management Branch: release version vs. develop version Snapshot of the whole system Prohibit further check-in before release
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Roadmap What is SCM Why do we need SCM Interesting SCM features
Source control vocabulary Code Sharing Branch Label
SCM tools GForge Conclusion
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Source Control Vocabulary
Update: obtain the latest versions of the code Check-out: obtain the writable version of files Check-in: commit the changes to files Lock/unlock: one only person may modify a file Integrate: combines the changes with others’ Add/delete: add/remove files to repositories Top-of-trunk: most updated
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Roadmap What is SCM Why do we need SCM Interesting SCM features
Source control vocabulary Code Sharing
Lock Sharing
SCM tools GForge Conclusion
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Code Sharing
Multiple people can work on the same source base without colliding ---
– (1) Lock: locks individual files so only one person at a time can modify it or
– (2) Merge: Allows multiple people to modify a source file and the system will automatically merge the changes (usually)
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Locking
Only one person can modify certain source files. Works fairly well if developers work on different
areas of the project and don’t conflict often Problem 1: People forget to unlock files when
they are done Problem 2: People work around locking by editing
a private copy and checking in when the file is finally unlocked - easy to lose changes.
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Merging
Several people can work on a file at once Before committing changes, each user
merges their copy with the latest copy in the database
– This is normally done automatically by the system and usually works, but you should not blindly accept the result of the merge
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Roadmap What is SCM Why do we need SCM Interesting SCM features
Source control vocabulary Code Sharing Branching
SCM tools GForge Conclusion
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Branching Brach sources for different purposes
When a new version ships, typically create a branch for maintenance
Companies ship several products from the same source base
Branching repository “fork” and branch off the base repository.
Double update: (manually) merge back changes in the branching repository
1.0
1.0.12.0
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Roadmap What is SCM Why do we need SCM Interesting SCM features
Source control vocabulary Code Sharing Branching Labeling
SCM tools GForge Conclusion
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Labeling
Label all the files in the source base that make up a product at each milestone
Just before and just after a major change (eg. changing several interfaces)
When a new version ships, want to fix fatal bugs in the original version.
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Roadmap What is SCM Why do we need SCM Interesting SCM features SCM tools GForge Conclusion
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CSM Tools
RCS – “revision control system” In most Unix system, only source control
CVS – “concurrent versions system” Free in linux, also support configuration management
SourceSafe well-integrated into other Microsoft developer products, but not on
other platforms ClearCase
commercial CSM tool SourceGorge (Gforge)
Projects are available for public discovery and development http://gforge.cis.cornell.edu/ (http://gforge.org)
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Helpful Rules
Archived Files Should Always Compile Update to get your codes “top-of-chunk” Code review Compile and run latest archived files *as a set*
before Check-in No Cheating (even “simple bug fixes”)
Release a lock after you are done. Don’t overwrite someone else’s code
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Roadmap What is SCM Why do we need SCM Interesting SCM features SCM tools GForge Conclusion
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GForge
GForge is an online SCM system SCM tools: create and control access to CVS and
Subversion Collaborating tool: forums and mailing lists; Access control: over the automatically created
repository depending on the role settings of the project File release, document management, news
announcements, surveys, task managements, etc.
Gforge in Cornell CIS https://gforge.cis.cornell.edu/
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Conclusion
SCM tools are Very Helpful GForge is a Good Project Tools Available
at CIS
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RCS
File management only Transaction model
– check out and lock
– edit
– check in and unlock Little support for binaries
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CVS
Built on top of RCS
– Therefore little support for binaries Database can be remote No locking: merge before commit Fast Integrates with emacs
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SourceSafe
Microsoft’s entry into the field Project-based Checkout-edit-checkin model Built-in web site creation tools Integrates with MSDEV
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Clearcase
Clearcase is configuration management on steroids
You create a view of the database with a config spec, which describes how to select files from the database.
When you set a view, Clearcase creates a virtual filesystem containing only those versions of the files selected by the config spec