Change set predecessor using cleartool

Eventually I'd like to find out how to diff a version in an UCM activity with the change set predecessor, using the command prompt, assuming there is more than one version for the same file in the activity.

I already know how to get all the versions of a file in an activity. In general I could diff the latest version in the set with the earliest-1, bu开发者_开发知识库t if the earliest version is the first version, because this is a new stream, then I'll have to figure the original stream. And that is also something I don't know how to accomplish.

A single cleartool command that receives a version and tells its predecessor will solve all my problems.

Any ideas?

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I don't know of a single command.

I do the a cleartool descr -pred would give you the predecessor of a current version, enabling you to get the version of said predecessor in the previous branch.

The extended pathname of a version is composed of the current branch (named ofter the current stream), and just before, of the branch from which the current branch has been created, which allows you to get the original stream name.

From there you have the version you need to make your diff.
However that will require a script.