I would like to know how to rename a branch specification (aka, a "branch mapping") in perforce. The P4V client does not allow you to edit the branch spec name.
Is it safe to just add another branch specification, copy the settings and remove the old one?
Yes. But you need to do an p4 integrate to get the files over. That is what p4v "copy or rename" does. Use the rename option, that also deletes the old files.
Perforce does not provide a mechanism to rename a branch specification. Perhaps they fear you may inadvertently break some scripts if you go and rename one?
Yes, it is safe to create a new one, copy the settings from the old and delete it (provided nothing is relying on a branch specification with that old name, of course).
Lack of branch spec renaming extends to all specs (users, groups, clients, labels, jobs, etc.). This is where the command line can come in handy:
p4 branch -o OLDBRANCH | sed -e "s,OLDBRANCH,NEWBRANCH," | p4 branch -i && p4 branch -d OLDBRANCH