How to convert .torrent file into magnet link?
Solution 1:
Rather late, but as suggested in the comments, the following produces a magnet link, with no further fiddling necessary:
transmission-show -m yourfiles.torrent
This program is shipped as part of the transmission-cli package on Debian derivatives, and part of the larger Transmission client.
Of course the .torrent file must be created beforehand, but that can also be done with a Transmission command, and it doesn't require a tracker (anymore):
transmission-create yourfiles