Installing gtg pulls out java, which is quite surprizing.

Turns out that pdftk-java is marked as a dependency. According to
upstream, this is not intentional and it is not even sure that the
features intended to work with the original pdftk still work with
pdftk-java

https://github.com/getting-things-gnome/gtg/issues/984

pdktk dependency should be marked as "optional" for now

Hi Ploum,

Without pdftk dependency, the `script_pocketmod` plugin would not work. So we
can't mark pdftk it as optional for now.

To avoid the java installation during gtg installation, I would suggest to
package the plugins as a separate deb package, which would itself be optional.
Would this makes sense to gtg users?

Best,

François