How to get rid of useless heads

[hg user]

So the only way to delete an head is to clone the repository forcing a
specific head and that will be the "main" repository ?

I ask it because I'm importing a cvs repository (hg convert) where the
owner (probably by error) created a never-used branch that shows up in
the hg repository as an head and as a branch...
the useless head causes obvious problems in merging...

Francesco