How to find out if a changeset contains another changeset?

[Jesse Glick]

Bryan O'Sullivan wrote:
> I think it would make sense to expose it.  I use it a lot.

+1. I did not know about the debugancestor trick until today.

My use case is similar: our build system appends `hg id` to a build_info 
file in the product, and I would like to quickly check whether a given 
binary build contains a given fix or not. I can compare dates, but this 
will not work for changes that were pushed to a "staging" repository and 
merged to the main repository later after verification.

I would suggest e.g. "hg contains $parent $child", printing "yes" or 
"no" unless -q given, also producing a 0 or 1 (resp.) exit status for 
use in scripts.