How to compare sets of changesets between 2 Mercurial branches?

I've got a (remote) Hg repository with a couple branches. I开发者_开发百科 want to verify that branch A has every changeset that branch B has (it may have more, and that's OK).

Is there an easy way to do this with just hg?

I can write a little shell script to do it, but it seems like the sort of thing that might come up a lot, so maybe there's an easy built-in way.

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This will show any ancestors of changeset b which are not an ancestor of changeset a:

hg log -r "ancestors(b) and not ancestors(a)"

This should show you which changes still need to be merged from B to A if you give the head of branch B for b, and the head of branch A for a.