In fact I think the whole ui-ext subdirectory should be in its own repo with its own version numbering scheme.

Also the artifactId of the plugin should not end in -plugin.

At the moment, Jenkins core has a dependency on the code in ui-ext/icon/module. This dependency may go away if we move Jenkins core to using CSS based icons (something I was planning on doing). For now though, lets assume the dep will not go away. Is there a dependency pattern like this already i.e. Jenkins core having a dependency on other Jenkins artifacts that do not live in https://github.com/jenkinsci/jenkins (i.e. live somewhere else in https://github.com/jenkinsci)?

Sure, core/pom.xml shows plenty of dependencies on libraries elsewhere in the jenkinsci org (or even other orgs, like kohsuke). So long as the dependency is not expected to be constantly changing (and in conjunction with changes to jenkins source files), this is fine.

merged in b55f5eb

Thanks, can now build Jenkins again without running out of PermGen space.

Did you mean for the plugin to be bundled in war/pom.xml?

I guess the answer would be "no", seeing as I'm not sure I follow the question. Are you telling me you're seeing it bundled somewhere it shouldn't be bundled, or suggesting it should be bundled as one of the artifactItems?

The latter, if you want it to be installed by default in Jenkins. Or is it only an optional download, or dependency of other plugins?

I had in mind that it would just be added as a plugin dependency as per the docs at https://github.com/jenkinsci/icon-shim-plugin .

I manually tested with the Credentials plugin (uploading the 2 plugins manually). Is there a good way of testing how it would ultimately work with the update center? I'm assuming (maybe wrongly) that the update center checks the plugin deps and will auto install this plugin for plugins that depend on it. Is that right? Maybe I can set up my own update center, or is that a PITA to do?

it would just be added as a plugin dependency

OK, then disregard my question.

the update center checks the plugin deps and will auto install this plugin for plugins that depend on it. Is that right?

Yes.