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Software Configuration Management

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Software Configuration Management

What is it?• Software Configuration Management is the process of tracking changes to software.

Why use it?• Maintain multiple branches and versions.• Recover previous versions.• Keep track of changes, ie, committed changes.

When to use it?• For text files: programs, data, and configuration files.• Supports binary files: Word and Excel files, etc.• In multi developer contexts: can assign blame for changes.

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Software Configuration Management

• Used in both single user and multi user environments.• There are two multi user paradigms

– Locked access – A single developer checks-out a copy of a file before modifying it. The modified file is then checked-in. During check-out only a single developer has access to the file.

– Concurrent access –Multiple developers work with their own copy of a file. Conflicts are resolved as the local copies are committed to the common repository.

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Software Configuration Management

• There are many implementations of version control software.– RCS (Revision Control System) is one of the earliest. It was developed along

with Unix. It is implemented as check-in/check-out.– CVS (Concurrent Versioning System) is built on top of RCS and implements a

concurrent access scheme. – Subversion is a newer and is designed as a replacement for CVS. It is more

easily deployed as a server. It is rapidly displacing CVS as the version control system of choice.

– Visual Source Safe is part of Microsoft Visual Studio. It is a check-in/check-out system and only runs on Windows.

– There are other open source and commercial implementations available.

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Subversion

• Runs on Linux, Unix, MacOS, and Windows.• Files, properties, and versioning information is maintained in a

repository.• The developer works with a copy located in a local working directory. • Subversion repositories are local or server-based.• The URL of the repository describes the access method

– file://... – a local file based repository

– svn://… - a repository using the built-in svnserver– svn+ssh://… - an svnserver with ssh used to control access (not a

tunnel)

– http://... – a web based repository, most common in multi user environments

• http://subversion.tigris.org/ home page• http://svnbook.red-bean.com/ Subversion Book

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Subversion

URL Notes• When using the file:// method, do not use it in multi user mode

while the repository is located on a shared network disk. It is unreliable and will eventually corrupt your repository.

• When using the http:// method, you can view the current head revision files using a normal browser.

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Subversion

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Subversion

• Plain SVN is a line mode system.– ex, svn update

• There are several GUI clients– http://subversion.tigris.org/links.html– TortoiseSVN is popular Windows client, explorer extension

• Download TortoiseSVN from– http://tortoisesvn.tigris.org/

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Subversion

Installation of TortoiseSVN• Download TortoiseSVN from

– http://tortoisesvn.tigris.org/

• Double click file – TortoiseSVN-1.5.3.13783-win32-svn-1.5.2.msi

• Installs as an explorer extension– special file icons for affected files

– added right-click menu items

– Start | Programs |TortoiseSVN

– Includes a differences program

• After installation explorer or computer must be restarted.

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Subversion

Use Cases• create a repository

• import initial files into new repository

• check out a repository into a working directory

• update a working directory

• change file svn properties

• add a new file to a repository

• commit changes to the repository

• checking status of files in working set

• listing files in repository

• show a files log entries

• revert to a previous version

• resolving conflicts

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Subversion

Create a Local Repository

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Subversion

Create a pair of directories/folders.

work is the working directory.

repos is the directory where repositories will reside.

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Subversion

Create the specific repository directory.

Use the TortiseSVN Explorer extension, right click the mouse on the repos folder.

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Subversion

A dialog box will appear asking for the type of repository to create. The choice is either a Berkeley Database file or a file-based repository. In most cases the file-based repository is best.

The line-mode equivalent issvnadmin create proj1 –fs-type fsfs

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Subversion

Now the repos directory is filled with folders and files that are used by Subversion to manage the repository.

The repository is still empty.

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Subversion

Import Project Files to Repository

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The initial set of files that are to be placed under version control are created in the work directory. In this example a single file, matmult.c, is created.

This is an optional step. It is used only if there is an existing project that is being added to a repository.

See slides on Adding Files to repository.

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Subversion

The next slide shows the contents of matmult.c.

In particular see line 5. The string $Id: $ identifies the revision number associated with the file. This string is updated to show the version id every time the working file is updated, if the appropriate property is set.

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Subversion

#include <stdio.h>#include <time.h>#define MAX 500

static char svnid[] = "$Id: $";

void printmat(double *a,int imax, int jmax) {

long int i,j;

printf("enter printmat\n"); for (i=0;i<imax;i++) { for (j=0;j<jmax;j++) { printf("%5.2f ",*(a + (jmax * i) + j)); } printf("\n"); }}

int main(int argc, char **argv) {

long int i,j, k; int iter; double a[MAX][MAX]; double b[MAX][MAX]; double c[MAX][MAX]; clock_t t1,t2;

for(i=0;i<MAX;i++) { a[i][i] = 2.0; b[i][i] = 3.0; }

t1 = clock();

for(iter=0;iter<10;iter++) {

for(i=0;i<MAX;i++) {

for(j=0;j<MAX;j++) {

c[i][j] = 0.0;

for(k=0;k<MAX;k++) {

c[i][j] = c[i][j] + a[i][k] * b[k][j];

}

}

}

}

t2 = clock();

printf("t1=%d, t2=%d\n",t1,t2);

printf("cpu time=%8.3f\n",(float)(t2 - t1)/CLOCKS_PER_SEC);

/*

printmat(c,MAX,MAX);

*/

}

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Subversion

The next step is to import the initial set of files into the repository.

Right-click the mouse on the work directory.

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Subversion

This dialog box requests the location of the repository. It is entered as a URL.

In this case the repository is a local directory so use the file:// form.

A web based URL might be http://svn/svn/proj

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This is the result of the import operation. It shows that one file has been added to the repository.

The current revision number is 1.

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The contents of the work directory can now be discarded.

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Check Out the Repository to a Working Directory

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Create a subversion working directory under revision control.

We will reuse the work directory.

To do this delete the contents of the work directory. At least the files that were added to the repository.

Now checkout the contents of the repository to the work directory.

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This dialog box is used to control what is checked out and to where.

The directory work will be created if it does not exist.

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For a server based working directory, the file work usually has the same name as the repository.

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This dialog box lists the files that were added to the working directory.

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Opening the working directory.

The TortoiseSVN extension results in changes to the file icons.

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Subversion

Additional information about revision controlled files can be displayed by using View/Details and then View/Choose Details…

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The dialog box that results from View/Choose Details…

The SVN parameters, if selected, will be displayed when View/Details is selected as the directory format.

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The result of selecting SVN Revision and SVN Status.

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Update a Working Directory

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Right click on directory or file and select SVN Update.

This will load the current version from the repository to the working directory.

When using a multi user repository it is a good idea to execute an update before working on the file.

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Set Subversion Properties

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To set properties on svn controlled files

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Subversion

To set properties on svn controlled files.

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Subversion

To set properties on svn controlled files.

The drop-down box shows the available properties.

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svn:eol-style

Subversion will set the end-of-line in a text file appropriate to the destination working directory.

svn:keywords

Informs Subversion to handle the keywords, eg, $Id: $, which will be updated when downloaded to the working directory.

svn:executable

Informs Subversion that the file is an executable file. It will set permissions on the working copy to allow execution.

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For this file svn:keywords has been set to Id and svn:eol-style has been set to native.

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Going back an looking at the work directory notice that the icon for the file matmult.c has changed. In this case it indicates that the svn properties for the file have changed.

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Add a New File to a Working Directory

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To add a new file, readme.txt, to the repository. Create the file in the working directory, then use svn add

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The dialog box that lists the files to be added to the repository. And the result of the add operation.

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The freshly added file has a “+” icon to indicate its status. Now set the properties of the file then commit it.

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The status of the working directory after the commit operation. Note that readme.txt is level 3 and matmult.c is level 2.

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Adding is the “better” way to put files into a repository.• Create the file in the working directory.• Add the file to the repository.• Set the appropriate properties.• Commit the file to the repository.

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Subversion

Commit Changes to Repository

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Now commit the changed file to the repository.

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The dialog that results from the commit operation allows you to enter a log message that describes the changes made.

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Subversion

The final dialog box verifying the update of the repository. The revision number is now 2. The icon for matmult.c reverts to the green check. Looking at the file matmult.c shows the following:

static char svnid[] = "$Id: matmult.c 2 2006-11-08 15:33:16Z latham $";

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Subversion

Listing the Contents of the Repository

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Subversion

The contents of the repository can be viewed by using the repository browser.

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The list of files in the repository.

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Show Log for File

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Subversion

To show a files log entries, right click the file and select TortoiseSVN | Show Log.

The window at the right shows every revision made that included a comment.

Use TortoiseSVN | Revision Graph for a complete list of all revisions.

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Revert to a Previous Version

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Subversion

Right click on the file to revert, then select the revision number that you want.

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Resolving Conflicts

(todo)