[Core] Add [p]listdisabled command (#3118)

* Update core_commands.py

* Create 3115.feature.rst

* Rename 3115.feature.rst to 3118.feature.rst

* Add a message if there's any disabled commands.

* Use the same format as [p]command disable/enable

* Make strings more i18n friendly.

* Flame's requested changes.

changelog.d/3118.feature.rst

@@ -0,0 +1 @@
+Adds a command to list disabled commands globally or per guild.

redbot/core/core_commands.py

@@ -33,7 +33,14 @@ from . import (
 )
 from .utils import create_backup
 from .utils.predicates import MessagePredicate
-from .utils.chat_formatting import humanize_timedelta, pagify, box, inline, humanize_list
+from .utils.chat_formatting import (
+    box,
+    humanize_list,
+    humanize_number,
+    humanize_timedelta,
+    inline,
+    pagify,
+)
 from .commands.requires import PrivilegeLevel
 
 
@@ -1877,6 +1884,53 @@ class Core(commands.Cog, CoreLogic):
         """Manage the bot's commands."""
         pass
 
+    @command_manager.group(name="listdisabled", invoke_without_command=True)
+    async def list_disabled(self, ctx: commands.Context):
+        """
+        List disabled commands.
+
+        If you're the bot owner, this will show global disabled commands by default.
+        """
+        # Select the scope based on the author's privileges
+        if await ctx.bot.is_owner(ctx.author):
+            await ctx.invoke(self.list_disabled_global)
+        else:
+            await ctx.invoke(self.list_disabled_guild)
+
+    @list_disabled.command(name="global")
+    async def list_disabled_global(self, ctx: commands.Context):
+        """List disabled commands globally."""
+        disabled_list = await self.bot._config.disabled_commands()
+        if not disabled_list:
+            return await ctx.send(_("There aren't any globally disabled commands."))
+
+        if len(disabled_list) > 1:
+            header = _("{} commands are disabled globally.\n").format(
+                humanize_number(len(disabled_list))
+            )
+        else:
+            header = _("1 command is disabled globally.\n")
+        paged = [box(x) for x in pagify(humanize_list(disabled_list), page_length=1000)]
+        paged[0] = header + paged[0]
+        await ctx.send_interactive(paged)
+
+    @list_disabled.command(name="guild")
+    async def list_disabled_guild(self, ctx: commands.Context):
+        """List disabled commands in this server."""
+        disabled_list = await self.bot._config.guild(ctx.guild).disabled_commands()
+        if not disabled_list:
+            return await ctx.send(_("There aren't any disabled commands in {}.").format(ctx.guild))
+
+        if len(disabled_list) > 1:
+            header = _("{} commands are disabled in {}.\n").format(
+                humanize_number(len(disabled_list)), ctx.guild
+            )
+        else:
+            header = _("1 command is disabled in {}.\n").format(ctx.guild)
+        paged = [box(x) for x in pagify(humanize_list(disabled_list), page_length=1000)]
+        paged[0] = header + paged[0]
+        await ctx.send_interactive(paged)
+
     @command_manager.group(name="disable", invoke_without_command=True)
     async def command_disable(self, ctx: commands.Context, *, command: str):
         """Disable a command.