Hi,

I am using `gbp dch` for generating my changelogs along with the
`Gbp-Dch:` filtering rules for several of my packages. When I get an MR,
I rarely remember to check how the commit messages will affect the
changelog.

I was therefore hoping that `gbp dch` could grow a new feature or
relevant documentation for using `gbp dch` in a CI pipeline to have it
maintain a comment (updating the same comment with each rebase/push)
with a preview of the changelog to be.

I have looked at `gbp dch --since` when seems like a decent starting
point, but the solution would likely be more complicated like having to
ignore commits from merges, accounting for existing snapshot entries,
and all commits being ignored.

Best regards,
Niels