Symbols in SRC-SCCS

The SCCS back end to SRC doesn’t support named symbolic references to numbered revisions, because SCCS masters don’t include a symbol table. This is one of the things RCS added.

Goddess help me, I’ve figured out how to shoehorn in this feature. And probably should not do it.

A nearly forgotten feature of both SCCS and RCS masters is the “descriptive text” field, one per master. When this was used it was normally set at master creation time to convey the purpose of the file for which the master is keeping history. But it can be modified after master-creation time.

The trick: swipe this field. if empty, and use it as an attribute-value dictionary encoded as a JSON object. If it’s nonempty, and doesn’t begin with a ‘{‘, exit with a warning rather than stepping on legacy data.

Now, in the SCCS back end, one attribute (initially the only one) can be a symbol table. Voila!

I shouldn’t do this. The odds of anyone wanting to use the SCCS back for production in 2016 are minimal. But I am tempted by a mad completist urge…