Good news this has been discussed, bad
news is that there is no implementation of this yet.
a slightly hacky workaround to save you pulling your hair out
every time you want to upgrade...
on your desktop (or machine with access to t'internet) download
the json file, then parse it and for each plugin listed download
it.
put them in a folder on a local web server (make sure the location
is the same as the path in the json file)
on the jenkins server alias the name of the machine that hosts the
plugins (
updates.jenkins-ci.com) that is in the json file with the
name of the local server with the plugins (e.g. edit /etc/hosts) .
et voila - less tedious work!
if you are feeling really clever you could write a script to do
this and to only fetch newly updated plugins so you don't have to
do it manually every time...
/James