Only do this, if you really need to try out the bleeding edge version of the wikipedia plugin. Otherwise you can install the latest released version like any other JOSM plugin.
Here is how you can install the current development version (not yet released, expect issues) of the
wikipedia JOSM plugin:
Expert modein the bottom left corner of the preferences dialog is checked.
Pluginstab. Click on
Configure…in the bottom right corner.
Addin the new dialog and enter the URL
https://josm.gitlab.io/wikipedia/snapshot/master/update-siteand confirm with
Download list, you have a new plugin in the plugin list:
wikipedia-dev. You can install that and it will be updated like the "normal" JOSM plugins.
Note: Please make sure that you don't have both the dev and the non-dev version (
wikipedia-dev) installed at the same time! This would lead to conflicts.