[p4] Merge into target from a prior changelist?

[Jeff Jensen]

Hi,

We're confused by results at our attempts to merge to a prior changelist.  What
is the correct sequence to accomplish that?

All the Googling and Perforce manual and tech tips reading we found were always
about *forward* movement of merging; we didn't find anything on our situation. 
Here is the scenario:

We integrated from //abc/main/... to //abc/release/integration/...
Obviously, this was a merge done at #head.  At the time, the changelist was some
number, say 12345.

Now we need to make the target the same as a previous changelist, say 11111.
So we tried:
p4 integ //abc/main/... at 11111 //abc/release/integration/...

But that did not update all the files correctly in target.  What else is needed?

My thinking is that Perforce saw that nearly all the changes from the sources
were already integrated to the targets, so only picked a couple of things (e.g.
adds of delete files).  Not sure about getting around that.

We tried -f, but that caused it to put all files again on the changelist, which
didn't seem right as many files had not changed (total file count was about
8200; less than 1000 had changed).  Resolving and then "revert unchanged" had
no effect, yet doing a diff on many files yielded "identical".

In the end, they deleted the target files and reintegrated.  Brute force, but
obtained the correct results!  :-(

So we're obviously missing something here...
Please enlighten!  :-)