"Generic SCM integration" support

[buddylott]

It would be nice to be able to use the command-line interface to do a small level of SCM integration with unsupported SCMs.

My preferred solution would be to have an SCM value that means "Custom-No-SCM interaction" and then be able to specify a change set id when using adddiffs command.

This would allow the changesets to be tracked the way Collaborator intendeds without actually needing direct SCM interaction.

[OlegGontarenko]

For now we are not planning to implement something like this.