+4  A: 

You can use hg commit --close-branch to mark a branch as closed:

http://www.selenic.com/mercurial/hg.1.html#commit

Closed branches will not show up in hg branches or hg heads by default (only if the -c/--closed option is specified), so I'm not sure how you're seeing "clutter"?

What exactly would you gain by merging things?

Amber
True enough that closing the branch stops it from showing up in hg branches, but it still shows up in the heads.
Mark Borgerding
Aha! I just realized that on newer versions of hg, the closed branch heads *ARE* hidden. So my "dead head" solution is overkill for a temporary problem.FYI. With version 1.3.1 the closed branches are incorrectly shown in "hg heads", in 1.5.1 they are correctly hidden.
Mark Borgerding