Ok, looking into this...
There is a slight issue with the upgrade script on line 28 where its missing an extra '../' and I've changed the wording of the offending confusing line. Updated on GitHub for M2.5 and M2.6 if you need it. I'll release when there are sufficient other changes to demand it.
With the M1.9 issue....
There is no backup and restore code for the format, so despite the fact that the images are placed in the backup file, the contents of the 'course_grid_icon' table which maps the images to the sections is not. Upon restore without this information the images are restored to the file system and the 'course/legacy' area, sub-folder 'icons' upon which the upgrade script could cope with, however because of the missing information in the 'course_grid_icon' table it does not have sufficient information to do its job. This means:
- That the M1.9 version would need to have a backup and restore script created for it. That I'd have to work out the complete restore process to decipher what table names are used as they have changed. Collapsed Topics did have something along the same lines in the past. The restore script would have to be placed in the M2.5 and M2.6 versions too as the restore process is a two stage one. From memory this is how it works (David Mudrak knows more): First the M1.x code is run to create a data set and then the M2.x restore code is run to create the course.
- That once '1' was completed you would have to backup again all your existing courses as the current backups would be invalid.
- Therefore because of '2' you would need to do this before upgrading to M2.x.
- If '1' existed both with the M1.x code in the M1.9 release and the 1.x restore code in the M2.5 and M2.6 releases then it would in theory you would still need the conversion script.
So as the current upgrade script works anyway when sites are directly upgraded and the existing backups you may have are invalid and there is a work-a-round. It would probably take me around a week to do this. Given that my past estimate for the image size change was 24 hours and given the unexpected issues its currently running at about 8.5 days then I'm sure you'll appreciate that perhaps I do not wish to spend my free time on it.
If anybody would like to tackle this as a learning exercise then please feel free to try. The M2.2 version of Collapsed Topics has backup and restore code working in combination for 1.x and 2.x for reference: https://github.com/gjb2048/moodle-format_topcoll/tree/MOODLE_22/backup.