## F.2. CVS Tree Organization

### Author

Written by Marc G. Fournier (`<scrappy@hub.org>`) on 1998-11-05

The command `cvs checkout` has a flag, `-r`, that lets you check out a certain revision of a module. This flag makes it easy to, for example, retrieve the sources that make up release 6_4 of the module `tc' at any time in the future:

    $ cvs checkout -r REL6_4 tc

This is useful, for instance, if someone claims that there is a bug in that release, but you cannot find the bug in the current working copy.

### Tip

You can also check out a module as it was at any given date using the `-D` option.

When you tag more than one file with the same tag you can think about the tag as “a curve drawn through a matrix of filename vs. revision number”. Say we have 5 files with the following revisions:

                 file1   file2   file3   file4   file5

                 1.1     1.1     1.1     1.1  /--1.1*      <-*-  TAG
                 1.2*-   1.2     1.2    -1.2*-
                 1.3  \- 1.3*-   1.3   / 1.3
                 1.4          \  1.4  /  1.4
                               \-1.5*-   1.5
                                 1.6

then the tag `TAG` will reference file1-1.2, file2-1.3, etc.

### Note

For creating a release branch, other then a -b option added to the command, it's the same thing.

So, to create the 6.4 release I did the following:

    $ cd pgsql
    $ cvs tag -b REL6_4

which will create the tag and the branch for the RELEASE tree.

For those with CVS access, it's simple to create directories for different versions. First, create two subdirectories, RELEASE and CURRENT, so that you don't mix up the two. Then do:

    cd RELEASE
    cvs checkout -P -r REL6_4 pgsql
    cd ../CURRENT
    cvs checkout -P pgsql

which results in two directory trees, `RELEASE/pgsql` and `CURRENT/pgsql`. From that point on, CVS will keep track of which repository branch is in which directory tree, and will allow independent updates of either tree.

If you are only working on the `CURRENT` source tree, you just do everything as before we started tagging release branches.

After you've done the initial checkout on a branch

    $ cvs checkout -r REL6_4

anything you do within that directory structure is restricted to that branch. If you apply a patch to that directory structure and do a

    cvs commit

while inside of it, the patch is applied to the branch and only the branch.