Document the --skip-plugins pgm init option

Change-Id: Id4dffc5c5060f7e1888797d34ff046b17015dc5a

Documentation/pgm-init.txt

@@ -9,6 +9,7 @@ init - Initialize a new Gerrit server installation
 	-d <SITE_PATH>
 	[--batch]
 	[--no-auto-start]
+	[--skip-plugins]
 	[--list-plugins]
 	[--install-plugin=<PLUGIN_NAME>]
 	[--install-all-plugins]
@@ -47,6 +48,13 @@ as necessary.
 	Location of the gerrit.config file, and all other per-site
 	configuration data, supporting libraries and log files.
 
+--skip-plugins::
+	Entirely skip installation and initialization of plugins. This option
+	is needed when initializing a gerrit site without an archive. That
+	happens when running gerrit acceptance or integration tests in a
+	debugger, using classes. Supplying this option leads to ignoring the
+	--install-plugin and --install-all-plugins options, if supplied as well.
+
 --list-plugins::
 	Print names of plugins that can be installed during init process.