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Most likely this task best is suited for using a script to be integrated into SmartGit as external tool.
Please try Help | Check for Latest Build in the SmartGit 8.1 preview
You already can select the commits and select Copy Message in SmartGit 8.1.
Why you are not using a plain compare (F4)?
Ich mean this dialog which pops up on Pull if pull.rebase is not configured yet in the .git/config file.

If you select the "Remember"-checkbox, pull.rebase = true will be added to ~/.gitconfig and you won't see this dialog again.
Customer support service by UserEcho
I've created a git-changelog.sh with following content:
and configured it in SmartGit: