SOFTWARE REVISION CONTROL WITH SUBVERSIONEvan Dickinson & Andy Huang – 9 March 2011

About revision control

Revision control tracks the changes you make to your code

Professional software developers can’t live without it.

Worth knowing if you write code at all, even if you’re not a “software person”

What it’s good for

Offsite backup Coordinate team work See changes

Undo the change that broke everything Freedom to experiment

You can always revert back to working code Organization

Don’t have to e-mail files, or make lots of copies.

Why you might not use it (for now) Learning takes (a bit of) time You’re using MAX/MSP

Photoshop, Illustrator, and other media files also have low payoff.

Several features work best with text files, not graphics.

But other features are still valuable, even with graphic files.

Plan B: Dropbox At least have a backup & central location

for all code

About Subversion (svn)

There are several tools for revision control subversion is one of them

svn is a command-line tool several graphical front-ends available

Free GUI and free hosting: SmartSVN (GUI – Mac, Windows, and Linux)

Demo. Free version has limited features, but they’re good enough.

Assembla.com (hosting)

Installation

Will be covered later It’s boring

Subversion Concepts

Repository

A server that stores your code Repository records:

Every change that’s made Who made it, when, and why

This is what assembla.com gives you Except they call repositories “spaces.” It’s

the same thing.

Working copy

A copy of the code on your laptop What you edit when you’re writing code You can have several working copies on

your computer Your teammates have their own working

copies

1 Repository & Many Working Copies

Repository(assembla.com server)

Clip art: all-free-download.com

Evan’s Computer

Two working copies, each in different folders

Andy’s Computer

One working copy

Revisions

When you get your code to a good stopping point, snapshot the change in a revision. Share the code with your team Gives a known-good point to go back to

Assembla also calls these “change sets”

Workflow Example

Stop when the code does what you want it to, and you’re ready to share

Step 1: Write your code

Make sure you’re changing what you think you’re changing Keep out temporary/testing changes SmartSVN: “Changes” button. Sometimes called “diff”

Step 2: Review your changes

Brings in newer changes (if any) Keeps you from overwriting your team members’ changes. SmartSVN: “Update” button

Step 3: Update

SmartSVN: “Commit” button Write a message that describes what you

changed

Step 4: Commit the Change

Done: Now your change is in the repository

Demo

Working with other people

Multiplayer Subversion

Workflow: Two people editing different files

Evan’s Working Copy

Repository Andy’s Working Copy

Revision: 5 Revision: 5 Revision: 5

Edit foo.pde Edit bar.pde

Commit revision 6 Revision: 6Repository has Evan’s change to foo.pde

Still at revision 5

Update to revision 6.Andy’s working copy has Evan’s change.

Edit bar.pde some more

Still at revision 6 Revision: 7Repository has Andy’s change to bar.pde

Commit revision 7

Update to revision 7.Evan’s working copy has Andy’s change

Two people editing one file

Best to do this rarely: I’m not saying “don’t” – sometimes you need to Use good communication:

Coordinate who’s doing what Avoid incompatible changes

But when you do: You can’t accidentally overwrite someone else’s

changes When you do an update (to get new changes):

Changes that don’t conflict are brought in automatically

Conflicting changes are highlighted for you to fix (see the section Conflict Resolution)

Demo

Links and Resources

SmartSVN: http://www.syntevo.com/smartsvn/ http://www.syntevo.com/smartsvn/

documentation.html Subversion: http://subversion.apache.org

/ Assembla: http://www.assembla.com Version Control with Subversion

Online book http://svnbook.red-bean.com/

Three steps:1. Sign up for an assembla.com

account2. Install SVN client3. Install SmartSVN

Installation

Assembla.com

Register an account Create a space

You want the free subversion repository The free options are hidden – click to

expand http://www.assembla.com/catalog

Install SVN Client – Mac

Install the MacOS X developer tools SVN is included These are on the MacOS X install DVD Also downloadable from

http://developer.apple.com/technologies/tools/

Is svn already installed? Open Terminal Run: which svn

Install SVN Client – Windows

Download it from: http://sourceforge.net/projects/win32svn/

Install & Configure SmartSVN Download from:

http://www.syntevo.com/smartsvn When you run it for the first time, it will

ask for paths to svnadmin and svnserve Mac:

/usr/bin/svnadmin /usr/bin/svnserve

Windows: c:\program files\subversion\bin\svnadmin c:\program files\subversion\bin\svnserve

Configure SmartSVN (part 2) It starts by offering to set up a repository

for you. Say no. (That offer assumes your repository

already has code in it.) Instead, you want: Import Project Into

Repository This is on the welcome window, or File ->

Import

SmartSVN: Import Project Into Repository

While importing into the repository, you’ll get to a step where it asks you which repository to import to. This is where you tell SmartSVN about your

assembla repository. Add a new repository and fill in the details

Here’s where you find the URL to use

A reminder of what all the buttons do

SmartSVN Overview

Check the selected file

If you select a directory, your action applies to all files in that directory. This is usually what you want.

If you select one file, you only work with that one file. That can be bad if you wanted to commit all your files, but just commit one by mistake.

Refresh

Load the latest data from the repository. Use this to see if there are newer revisions.

Update

Two uses:1. Grab the latest code from the

repository.2. Change the working copy to an

older revision. (This is useful for figuring out if a problem you just found exists in older revisions.)

Commit

Send the contents of your working copy to the repository.

None of the changes you make to your working copy are applied to the repository until you do a commit.

Add

Tells subversion to track changes to the selected file (or directory).

Subversion only tracks the files you tell it to track. Files you don’t add won’t be in your repository.

Remove

Tells subversion stop tracking changes to the selected file (or directory).

Old versions of the file will remain available in the repository. But the file will no longer be in new versions of the repository.

Move (and Rename)Move and/or rename a file.

SmartSVN gets confused if you move/rename files from the Finder (or Windows Explorer)

In this example, we’ve renamed Arm.pde to Leg.pde. Until you do a commit, Arm.pde will show up as “removed.”

Revert

Throws away the changes you’ve made in your working copy. Reverts a file (or directory) back to the way it was when you did an update.

Delete

Deletes a file. Only use this on files that are not tracked by subversion.

Changes

Shows the changes you’ve made in the file.

Annotate

Shows who wrote each line of the file, and when.

Log

Shows the list of revisions

Fix and Graph

These are advanced features. You don’t need them.

Conflict Resolution

Conflicts

Conflicts occur when two people make incompatible changes to one file at the same time.

Usually, it’s OK for two people to change the same file, as long as they change different parts of the file. But if the changes are too close together, they conflict.

Conflicts are rare. But if they happen to you, here’s what to do. If you communicate with your team about

who’s changing what, you can avoid conflicts in the first place.

What conflicts look like

We did an update and – oh no! – there are conflicts.

The new files are:• .mine – the file you edited, as it was before the

update• .r3 – the predecessor for your changes. (That is,

the file as it was before you started editing.) The number will be different in your case.

• .r6 – the newest version of the file.

Fixing conflicts

The left pane shows your file, before the update.

The center pane is the file where you’ll resolve the conflicts. Right now, it has both changes in it, which is no good.

Bring up the conflict solver with Tools -> Conflict Solver

The right pane shows the newest version in the repository.

We got a conflict because two people changed the same line, at the same time.

Fixing conflicts, continued

Use the Take Left and Take Right buttons to choose which code to use.

Fixing conflicts, continued

Here, we used Take Right to copy the changes from the right-hand side to the middle. The conflict is now resolved, and we can save the file and commit it.