[TxMt] SVN?

[Charilaos Skiadas]

On Mar 29, 2007, at 3:50 PM, James Edward Gray II wrote:

> On Mar 29, 2007, at 2:32 PM, Rob McBroom wrote:
>
>> Most of the changes you make are small and stupid and not worth  
>> committing.
>
> I strongly disagree with that.
>
> Subversion is a tool for working with changes, much like Address  
> Book is a tool for working with addresses.  It has numerous  
> operations for those changes including reporting on what was  
> changed, by who, when, and the reason they gave for the change.  Of  
> course, it can only help you with what it knows about, just like  
> your Address Book.
>
> The more you get into version control, the more you learn that  
> those smaller changes are exactly what you want.  You want to get  
> it down to where each commit does just one thing, whether that's  
> adding a new feature, fixing a bug, or just some copyediting.   
> Subversion then becomes even more powerful because you can work  
> with these changes individually.

Let me add a couple of things to all this:
1) Every svn commit comes with four key pieces of information: WHEN  
it happened, WHO did it, a DESCRIPTION of what the commit is about  
and WHAT has changed. You can then search for all this information.  
In the context of a project involving more than one person, all these  
are absolutely critical things, especially if the members in the team  
change. Case in point is all the bundles in TM. We can actually  
search in the repository to find who added a new command or changed a  
line in the code, and what their rationale behind it was. (This is  
btw why it is very important that the commit messages describe the  
situation of the change and why it happened, instead of the change  
itself)
However, even in the context of a single person, it is a great source  
of information, especially when you get back to a project you were  
working on 2 years ago or so. It's the same reason we add comments to  
source code, because the actual code does not reveal much about the  
*context* in which it was written and the considerations that were  
going on through the developer's mind at the moment.

You can also determine, within a particular file, exactly who was the  
last person to change each individual line and when.

2) I would think that it is particularly important that you have a  
subversion system exactly when you do web stuff, where you need to  
check things on the actual server often. With a subversion system,  
you can update the server after you've committed the changes, and  
then if there are problems simply revert to the previous, known-to-be- 
working, version until you've worked out what went wrong. Even  
better, you have the production server and a development server. So  
after you commit your changes, you update the development server and  
test there, and if things work out then you also update the  
production server. The update command in this context would be a  
simple "svn up" running in the servers, regardless of what changes  
you've made, instead of a bunch of scp/rsync's. You can just turn it  
into a textmate command and activate it with the click of a button.

On the other hand, if you manually copy your changes to the server  
and then it turns out you have made a mistake and this version is not  
workable, how do you revert to the previous version? You'll have to  
figure out exactly what you changed and change it back. That would  
seem terribly inefficient to me, when a simple "svn revert" would do.

I am however not a web developer, so perhaps there is something I  
misunderstand there, otherwise I really don't see how anyone could  
work on a big web project without a versioning system. A versioning  
system provides a complete journal of what happened when and why,  
things that can be invaluable. I've actually started using it for  
math papers as well (well, my thesis actually. But I am thinking it  
could be a really nice way to collaborate, though a paper has  
somewhat different problems not really solved by a versioning system.  
Anyway, I digress ;) )

> James Edward Gray II

Haris Skiadas
Department of Mathematics and Computer Science
Hanover College