View to modify an old configuration

This config spec allows developers to modify a configuration defined with version labels:

(1): element * CHECKEDOUT
(2): element * .../r1_fix/LATEST
(3): element * R1.0 –mkbranch r1_fix

Note the following points about the configuration:

Elements can be checked out (Rule 1).
The checkout command creates a branch named r1_fix at the initially selected version (the auto-make-branch clause in Rule 3).

A key aspect of this scheme is that the same branch name, r1_fix, is used in every modified element. The only administrative overhead is the creation of a single branch type, r1_fix, with the mkbrtype command.

This config spec is efficient. Two rules (Rules 2 and 3) configure the appropriate versions of all elements:

For elements that have been modified, this version is the most recent on the r1_fix subbranch (Rule 2).
For elements that have not been modified, this version is the one labeled R1.0 (Rule 3).

The following figure illustrates these elements.

The version trees of the modified and not modified views of an unnamed element are shown. — Figure 1: Making a change to an old version

The r1_fix branch is a subbranch of the main branch. But Rule 2 handles the more general case, too. The ... wildcard allows the r1_fix branch to occur anywhere in the version tree of any element, and at different locations in the version trees of different elements.