Add tab to listing chooser for multi explore subreddit.

r2/example.ini

@@ -612,3 +612,5 @@ goldvertisement_has_gold_blurbs = "**“Exquisite!”**  \nGrab a drink
 listing_chooser_sample_multis = /user/reddit/m/hello, /user/reddit/m/world
 # multi of subreddits to share with gold users
 listing_chooser_gold_multi = /user/reddit/m/gold
+# subreddit showcasing new multireddits
+listing_chooser_explore_sr = multis

r2/r2/lib/app_globals.py

@@ -231,6 +231,7 @@ class Globals(object):
         ],
         ConfigValue.str: [
             'listing_chooser_gold_multi',
+            'listing_chooser_explore_sr',
         ],
         ConfigValue.dict(ConfigValue.int, ConfigValue.float): [
             'comment_tree_version_weights',

r2/r2/lib/pages/pages.py

@@ -239,7 +239,10 @@ class Reddit(Templated):
             show_chooser and
             c.render_style == "html" and
             c.user_is_loggedin and
-            isinstance(c.site, (DefaultSR, AllSR, ModSR, LabeledMulti))
+            (
+                isinstance(c.site, (DefaultSR, AllSR, ModSR, LabeledMulti)) or
+                c.site.name == g.live_config["listing_chooser_explore_sr"]
+            )
         )
 
         self.toolbars = self.build_toolbars()
@@ -4138,6 +4141,12 @@ class ListingChooser(Templated):
             multis.sort(key=lambda multi: multi.name.lower())
             for multi in multis:
                 self.add_item("multi", multi.name, site=multi)
+
+            explore_sr = g.live_config["listing_chooser_explore_sr"]
+            if explore_sr:
+                self.add_item("multi", name=_("explore multis"),
+                              site=Subreddit._by_name(explore_sr))
+
             self.show_samples = not multis
 
         if self.show_samples: