Hi,

check the manifest.xml from thewire_tools plugin, somewhere it says requires => thewire. You could change this to the name of your plugin.

I won't garantee that is works though ;)

Or you could tell in the manifest of your plugin "provides" => thewire see https://github.com/Elgg/Elgg/blob/master/docs/info/manifest.xml#L104

Override forms/comment/save view and change input/longtext used there to input/plaintext

Override forms/comment/save view and change input/longtext used there to input/plaintext

 This is nice. It works very well. Is it possible (how?) to keep the "Embed Content" link along with plain text input?

Well, deleting the system-cache folder in the data fixed the problem.
All site runs fine.

However, i still get the fatal error on upgrade.php

Version is 1.8.15

You have mixed files from newer release. In 1.8.15 there shouldn't be upgrade script that's being called: https://github.com/Elgg/Elgg/tree/1.8.15/engine/lib/upgrades

It was added in 1.8.17

Probably it's best idea to upgrade your install to latest 1.8.19 version as there were few security fixes in the meantime.

That fatal error means you do not have all the necessary files updated for that release.