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Sun WorkShop TeamWare 2.1 User's Guide

Introduction to Versioning

Coordinating write access to source files is important when changes will be made by several people. Maintaining a record of file updates allows you to determine when and why changes were made.

The source code control system (SCCS) allows you to control write access to source files and monitor changes made to those files. SCCS allows only one user at a time to update a file, and it records all changes in a history file.

TeamWare Versioning is a GUI to SCCS. Versioning allows you to manipulate files and perform SCCS functions without having to know SCCS commands. It provides an intuitive method for checking files in and out, as well as displaying and moving through the history branches.

With Versioning, you can:

Versioning helps you perform these tasks and expedites the progress of concurrent development projects.

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.

Situations can arise, however, when it is necessary to create an alternative branch on the tree. Branches can be used, for instance, 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 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).

Deltas and Versions

When you check in a file, SCCS records only the line-by-line differences between the text you check in and the previous version of the file. This set of differences is known as a delta. The file version that you initially checked out was constructed from a set of accumulated deltas. The terms delta and version are often used synonymously; however, their meanings are not the same. It is possible to retrieve a version that omits selected deltas.

History Files

When you initially put a file under SCCS control, a history file is created for the new SCCS file. The initial version of the history file uses the complete text of the source file. The initial history file is the file that further deltas are compared to. Owing to its prefix (s.), the history file is often referred to as the s.file (s-dot-file).

SCCS Delta ID (SID)

An SCCS delta ID (SID) is the number used to represent a specific delta. This is a two-part number, with the parts separated by a dot (.). The SID of the initial delta is 1.1 by default. The first part of the SID is referred to as the release number, and the second, the level number. When you check in a delta, the level number is incremented automatically.