next-status: Include a list of trees with duplicate commits

It's possibly interesting to report trees that are duplicating commits,
this tends to be a combination of trees that routinely cherry pick fixes
instead of merging them up and transient issues with trees that upstream as
patches rather than pull requests.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Breno Leitao <leitao@debian.org>