Branches

You can picture the deltas applied to an SCCS file as nodes of a tree with the initial version of the file as the root. The root delta is numbered 1.1 by default. These two parts of the SCCS delta ID (SID) are the release and level numbers. Successive deltas (nodes) are named 1.2, 1.3, and so forth. This structure is called the trunk of the SCCS delta tree. It represents the normal sequential development of an SCCS file.

It may be necessary to create an alternative branch on the tree. Branches can be used to keep track of alternate versions developed in parallel, such as for bug fixes.

The SID for a branch delta consists of four parts: the release and level numbers and the branch and sequence numbers, or release.level.branch.sequence. The branch number is assigned to each branch that is a descendant of a particular trunk delta; the first branch is 1, the next 2, and so on. The sequence number is assigned, in order, to each delta on a particular branch. Thus, 1.3.1.1 identifies the first delta of the first branch derived from delta 1.3. A second branch to this delta would be numbered 1.3.2.1 and so on.

The concepts of branching can be extended to any delta in the tree. The branch component is assigned in the order of creation on the branch, independent of its location relative to the trunk. Thus, a branch delta can always be identified from its name. While the trunk delta can be identified from the branch delta's name, it is not possible to determine the entire path leading from the trunk delta to the branch delta.

For example, if delta 1.3 has one branch, all deltas on that branch will be named 1.3.n. If a delta on this branch has another branch emanating from it, all deltas on the new branch will be named 1.3.2.n. The only information that can be derived from the name of delta 1.3.2.2 is that it is usually the second chronological delta on the second chronological branch whose trunk ancestor is delta 1.3. In particular, it is not possible to determine from the name of delta 1.3.2.2 all of the deltas between it and its trunk ancestor (1.3).