In #2445, I lifted out the fork button into its own template, but did
not update it properly. This resulted in the fork button's counter not
displaying, and pointing to the wrong place too.
This patch updates the template to account for it moving to a separate
file, and also adds test cases to verify the button is display as it
should be.
Fixes#2494.
Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
aef0b024b7