SVN - When you tag a working copy is it still a cheap copy?

Question

Using Subversion, in my working copy I make a minor modification (update a version number). I would then like to tag my working copy. Would this tag still be a cheap copy with the modification, or would SVN duplicate the files? I would hate to see my repository grow enormously in size because I'm trying to save a version number change.

The reason I ask about creating a tag that contains a modification rather than committing then tagging involves my build server. The build server creates a CCNetLabel which I use to update the version numbers of my projects (AssemblyInfo.cs). When the build is successful it creates a tag. When I use ForceBuild the tag is based on the working copy which would contain the modified version number. I want the tag to contain the appropriate version number.

note: It's debatable if I'm creating a branch or a tag, however SVN does not make a distinction between the two.

Answer 1

It depends. If your working copy is up to date (all nodes have the same revision) it is just as cheap as tagging from the repository.

For every file/directory (or actually subtree) with a different revision than its parent additional data will be added. And if you have local modifications even more data will be added.

But it is still reasonable cheap: It doesn't duplicate any files that are already in the repository.

Answer 2

From the subversion description

• Branching and tagging are cheap (constant time) operations. There is no reason for these operations to be expensive, so they aren't. Branches and tags are both implemented in terms of an underlying "copy" operation. A copy takes up a small, constant amount of space. Any copy is a tag; and if you start committing on a copy, then it's a branch as well. (This does away with CVS's "branch-point tagging", by removing the distinction that made branch-point tags necessary in the first place.)

Note! I just noticed that Subversion has been moved into the Apache project organization

Answer 3

Quite an out of date post but worth mentioning for anyone visiting that the answer stating you can only 'You can only tag data that has already been committed into the repository...' committed work is not completely accurate (at least not now).

You can tag a working copy, which could contain mixed revisions and even switched directories as well as local modifications.

As for cheapness, yes it should still be cheap as Subversion will branch for you, then overlay your working copy changes into the repo, saving as much space as possible

Answer 4

Creating a tag or a branch in subversion is very cheap. The files will not be copied. All that happens is that a new revision will be created, the content of which basically just contain a pointer to where the tag was copied from. This will be the same size for a tag of a project with one small file or for one with a million big ones.

When you say "tag my working copy", do you mean "tag my working branch"? You can only tag data that has already been committed into the repository somewhere, not your local uncommitted changes.