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In version 19.1 one can show/hide merged commits if "Follow only first parent" is selected.

If you need more worktree commands than in 18.2 available, please request them separately.

Who would volunteer to co-operate with us on a long-term base to maintain the language of their choice (except of German and English)?

It should be possible to copy the second file and then invoke SmartSynchronize on the first file. In the occurring welcome dialog the copied file should be preselected in the second file input field.