Categorise commits in merge collectively

[TTitcombe]

Is your feature request related to a problem? Please describe. Sometimes (often) it takes several commits to make one complete feature change. as doculog currently works, this create false positive/duplicate features in the changelog. doculog should interpret

Describe the solution you'd like A clear and concise description of what you want to happen.

Describe alternatives you've considered None

Additional context N/A