ReDisposition is Firefox extension to override HTTP header Content-Disposition.
Host at AMO, fully reviewed by AMO editors.
https://addons.mozilla.org/firefox/addon/redisposition/
Also host at AMO, development channel
https://addons.mozilla.org/firefox/addon/redisposition/versions/
This repository directory structure is the content of Firefox extension xpi file.
So just checkout/download the code, archive all the files(not the toplevel folder) to zip file.
Then rename the filename suffix ".zip" to ".xpi", install it.
The translation files are host at Transifex.
If you want to help translating this project into your native language, check the page
https://www.transifex.com/projects/p/redisposition/