setting revision range when merging related branches

Hello –

I have a merging question when branches are releated.  In most cases when we merge 2 branches I set the revision range to be merged of the source branch from its first revision to the latest.  This does not make sense when merging to a branch which is the child of the source branch.  In this case you would want to start your revision range from the revision where the child branch was created.  There would not be any point in applying source revisions to a target from a point in time where the 2 branches were the same code line. 

My thought on how to do this was to take the history of the target branch and trace back (stop on copy set to false) and trace back to see if the target has the same URL as the parent source at some point.  This would then be the starting point for the revision range of the merge.  The problem here is this is not that straight forward, the history for the target contains a Map of changed paths.  It is not that simple to get back to URLs to compare to the URL of the source branch.  In going down this path I am thinking there must be an easier way to do this. 

So the question is what is the correct way to set the revision range for a merge where the target of the merge is a child branch of the source for the merge? 

Thanks in advance for the help. 

Scott A Carter

Software Configuration Management Engineer