What do “branch”, “tag” and “trunk” mean in Subversion repositories?

Question

I\'ve seen these words a lot around Subversion (and I guess general repository) discussions.
I have been using SVN for my projects for the last few year

Answer 1

I'm not really sure what 'tag' is, but branch is a fairly common source control concept.

Basically, a branch is a way to work on changes to the code without affecting trunk. Say you want to add a new feature that's fairly complicated. You want to be able to check in changes as you make them, but don't want it to affect trunk until you're done with the feature.

First you'd create a branch. This is basically a copy of trunk as-of the time you made the branch. You'd then do all your work in the branch. Any changes made in the branch don't affect trunk, so trunk is still usable, allowing others to continue working there (like doing bugfixes or small enhancements). Once your feature is done you'd integrate the branch back into trunk. This would move all your changes from the branch to trunk.

There are a number of patterns people use for branches. If you have a product with multiple major versions being supported at once, usually each version would be a branch. Where I work we have a QA branch and a Production branch. Before releasing our code to QA we integrate changes to the QA branch, then deploy from there. When releasing to production we integrate from the QA branch to the Production branch, so we know the code running in production is identical to what QA tested.

Here's the Wikipedia entry on branches, since they probably explain things better than I can. :)