Understanding Subversion (SVN) for Collaboration in Software Development
This lecture outlines the essentials of Subversion (SVN), a centralized version control system designed for sharing information among multiple users. Key topics include the structure of repositories, working copies, and essential commands for managing files. We discuss problems with file sharing, including the Lock-Modify-Unlock model and the Copy-Modify-Merge strategy that SVN uses. The lecture also covers administrative tasks such as committing changes, creating repositories, and using tools to track modifications and resolve conflicts. This is crucial for collaborative software development projects.
Understanding Subversion (SVN) for Collaboration in Software Development
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Presentation Transcript
CS311 – Lecture 08 Outline • Subversion (SVN) • *All information taken from “SVN Book” O’Reilly CS 311 - Operating Systems I
Software needed • SVN is installed in flip server • Windows users use Tortoise SVN. • Linux and MAC users visit this website for installation instructions. - http://subversion.tigris.org/ CS 311 - Operating Systems I
What is SVN? • Centralized system for sharing information. • Data stored in the system in the form of a file system tree. • Any number of users with access to the system can read-write data. • When user writes data into repository it becomes publicly available. CS 311 - Operating Systems I 3
Difference between file server • What happens when a user updates a file which is already being accessed by another? CS 311 - Operating Systems I
Problems with file sharing CS 311 - Operating Systems I
Lock-Modify-Unlock • What are the problems with this model? CS 311 - Operating Systems I
Problems with Lock-Modify-Unlock • Administrative problems • Unnecessary serialization • Creates a false sense of security • Restrictive CS 311 - Operating Systems I
Copy-Modify-Merge solution CS 311 - Operating Systems I
Copy-Modify-Merge Solution CS 311 - Operating Systems I
Merits and demerits of copy-modify-merge solution • Merits • No problem of serialization. • Administering the files much easier. • Resolving conflicts • Demerits • Not all type of files can be merged (Eg. Audio) CS 311 - Operating Systems I
Subversion • Uses copy-modify-merge system but still occasionally implements locks on a file. • Very helpful for collaborative work. • In-built tools to view changes in a file and resolve conflicts. • Ability to browse through every revisions a file has gone through and also revert to any revision. • In-built tools to merge changes. CS 311 - Operating Systems I
SVN Repository and Working Copy • Repository is a place in the file system where all data exists. • Working copy is a place in the file system where modifications are done to the data and then updated to the repository. • To get a working copy use “svn checkout path-to-repository”. • If the repository resides on a network use “http://path-to-repository” or if in a local system use “file:///path-to-repo”. CS 311 - Operating Systems I
Working Copies • “.svn” folder in the working copy called the administrative directory. • It holds all changes, outdated revisions, the information about the working copy, etc. • To get the info about working copy use “svn info” from inside the working copy. $ svn checkout http://svn.example.com/repos/calc A calc/Makefile (“A” means files are added) A calc/integer.c A calc/button.c Checked out revision 56. $ ls -A calc Makefile button.c integer.c .svn/ CS 311 - Operating Systems I
Publishing changes • To publish changes use “svn commit” • $ svn commit button.c -m "Fixed a typo in button.c." • Sending button.c • Transmitting file data . • Committed revision 57. • When your teammates now update their working copies using “svn update” • $ svn update • U button.c • Updated to revision 57. • Always remember to update your working copy before committing changes to avoid conflicts. CS 311 - Operating Systems I
How working copy tracks changes • .svn folder is the administrative folder. • It keeps track of these • What revision are your files currently on • Last update of working copy • “svn log” command gives you the history of changes. CS 311 - Operating Systems I
Creating a SVN Repository • To create a SVN repository use • svnadmin create repo-name • Ex: svnadmin create /var/svn/newrepos • To add files into the repository use • svn import files path-to-repo • svn import mytree file:///var/svn/newrepos/some/project • -m "Initial import" • Adding mytree/bar.c • Adding mytree/subdir • Adding mytree/subdir/quux.h • Committed revision 1. CS 311 - Operating Systems I
Making changes to repository • To inform svn repo that you are making changes use the svn command. • svn add file #add file to repo • svn delete file #delete file from repo • svn copy file1 file2 • svn move file1 file2 • svn mkdir folder • After making all changes to repository do not forget to commit the changes (svn commit) • Use svn help command to know more about commands. CS 311 - Operating Systems I
Status of files in working copy • To know the status of files in the working copy use command “svn status” • ? scratch.c # file is not under version control • A stuff/loot/bloo.h # file is scheduled for addition • C stuff/loot/lump.c # file has textual conflicts from an update • D stuff/fish.c # file is scheduled for deletion • M bar.c # the content in bar.c has local modifications CS 311 - Operating Systems I
Using svn diff • diff finds the modifications done to a file. • Also used to generate patch. (svn diff file > patch) $ svn diff bar.c --- bar.c (revision 3) +++ bar.c (working copy) @@ -1,3 +1,2 @@ +#include <stdio.h> int main(void) { - printf("Sixty-four slices of American Cheese...\n"); + printf("Sixty-five slices of American Cheese...\n"); return 0; } CS 311 - Operating Systems I
