Wrote this for a project some friends and I worked on. All work in our case was done in "Default" with merges to Release, and then possibly Deploy.

Because of how Mercurial handles tags between branches you must add these lines to your hgrc

vim .hg/hgrc

[merge-tools]
merge-tags.executable = cat
merge-tags.args = $local $other | sort -u >> $output

[merge-patterns]
.hgtags = merge-tags

Good! It's gross, heavy handed and probably shouldn't be written in bash. Improve it and let me know.