If you look at merge commits, it is difficult to get an idea of what was merged when all commits look like this:

Merge pull request #N in project/repository from user/repository:branch into master.
Merge pull request #K in project/repository from user/repository:branch into master.
Merge pull request #J in project/repository from user/repository:branch into master.

I have no problem with making this a default merge commit message, but I'd like to override it so I can see messages like:

Fixes issue #N.
Adds feature XYZ.
...