The way I would do this is to build up the set of changes I wanted in my workspace using a combination of p4 edit, sync, and resolve. The basic process would be:
- Sync to change A (assuming it starts the sequence)
- Open everything for edit
- Sync to change B-1 (this will schedule a resolve )
- Run p4 resolve and ignore the changes (-ay)
- Sync change B ( this will schedule a resolve )
- Resolve change B handling any conflicts
- Sync to change C-1
- Resolve and ignore the changes
- Sync change C
- Resolve and merge in the changes
- Diff against head