DEV: Clean up .gitignore (#12981)

(inspired by martin-brennan's recent adventure with `tags` exclusion)

**tl;dr: some of it is obsolete, some is dev-env specific and should live in *your* ~/.gitignore.**

---

To enable global gitignore (`~/.gitignore`) run:
```bash
git config --global core.excludesFile '~/.gitignore'
```

Then create that file and add your VIM/VSCode/Sublime/Emacs/Eclipse/RubyMine/JetBrains/macOS/Arch/Windows 95-specific stuff.

---

Reasons for removal:

* `bin` - never really ignored, all the files are checked in
* `.DS_Store`, `._.DS_Store` - OS specific
* `.sass-cache/*`, `/.bundle`, `/bundle/*`, `/cache`, `/logfile`, `!/plugins/discourse-nginx-performance-report`, `MiniProfiler/Ruby/rack-mini-profiler-2.0.1a.gem`, `config/fog_credentials.yml`, `/public/stylesheet-cache/*`, `script/download_db`, `script/refresh_db`, `config/version.rb` - no longer used?
* `/log/*.log` - covered by /log
* `bootsnap-load-path-cache`, `bootsnap-compile-cache` - bootsnap now keeps its ~~trash~~ temporary files in `/tmp`
* `/.project`, `/.buildpath`, `/.byebug_history`, `/.idea`, `discourse.sublime-workspace`, `*~`, `*.swp`, `*.swo`, `*.swm`, `config/multisite1.yml`, `.rvmrc`, `.ruby-version`, `.ruby-gemset`, `.rbenv`, `bundler_stubs/*`, `*.db`, `*.iml`, `*.swn`, `/package-lock.json`, `.vscode`, `.envrc`, `tags` - dev-env specific, see the note at the top of the commit

.gitignore

@@ -1,33 +1,26 @@
-# See http://help.github.com/ignore-files/ for more about ignoring files.
+/copyright
-#
+/coverage
-# If you find yourself ignoring temporary files generated by your text editor
+/data
-# or operating system, you probably want to add a global ignore instead:
+/log
-#   git config --global core.excludesfile ~/.gitignore_global
+/tmp
 
-.DS_Store
+/.env
-._.DS_Store
+/.procfile
-dump.rdb
+/dump.rdb
 
-bin/*
+/config/discourse.conf
+/config/discourse.pill
+/config/multisite.yml
+# `discourse_dev` gem
+/config/dev.yml
 
-data/
+/public/assets
-
+/public/backups
-.sass-cache/*
+/public/csv
-public/csv/*
+/public/fonts
-public/plugins/*
+/public/plugins
-public/tombstone/*
+/public/tombstone
-
+/public/uploads
-# Ignore bundler config
-/.bundle
-/cache
-/coverage/*
-
-/public/assets/*
-/public/tombstone/*
-/bundle/*
-
-config/discourse.pill
-config/discourse.conf
 
 # Ignore the default SQLite database and db dumps
 *.sql
@@ -38,120 +31,29 @@ config/discourse.conf
 /db/schema.rb
 /db/schema_cache.yml
 
-# Ignore all logfiles and tempfiles.
+# Plugins except for the bundled ones
-/log/*.log
-/tmp
-/logfile
-log/
-bootsnap-load-path-cache
-bootsnap-compile-cache/
-
-# Ignore plugins except for the bundled ones.
 /plugins/*
-!/plugins/lazy-yt/
-!/plugins/poll/
 !/plugins/discourse-details/
-!/plugins/discourse-nginx-performance-report
+!/plugins/discourse-local-dates
 !/plugins/discourse-narrative-bot
 !/plugins/discourse-presence
+!/plugins/lazy-yt/
+!/plugins/poll/
 !/plugins/styleguide
-!/plugins/discourse-local-dates
 /plugins/*/auto_generated/
 
 /spec/fixtures/plugins/my_plugin/auto_generated
 
-# Ignore Eclipse .project file
+/vendor/bundle/*
-/.project
-
-# Ignore Eclipse .buildpath file
-/.buildpath
-
-# Ignore byebug history
-/.byebug_history
-
-# Ignore RubyMine settings
-/.idea
-
-# Ignore gem that is copied in
-MiniProfiler/Ruby/rack-mini-profiler-2.0.1a.gem
-
-discourse.sublime-workspace
-
-# Vim temp files
-*~
-*.swp
-*.swo
-*.swm
-
-# don't check in multisite config
-config/multisite.yml
-# don't check in my renamed multisite config as well :)
-config/multisite1.yml
-config/fog_credentials.yml
-
-/public/fonts
-/public/uploads
-/public/backups
-/public/stylesheet-cache/*
-
-# Scripts used for downloading/refreshing db
-script/download_db
-script/refresh_db
-
-# .procfile
-.procfile
-
-# .env, local environment variables for use with foreman
-.env
-
-# exclude our git version file for now
-config/version.rb
-
-# ignore the Ruby Version manager (rvm)
-.rvmrc
-.ruby-version
-.ruby-gemset
-.rbenv
-bundler_stubs/*
-
-vendor/bundle/*
-*.db
-
-# ignore jetbrains ide file
-*.iml
-
-# vim swap
-*.swn
-
-# ignore nodejs files
-node_modules
-/package-lock.json
-
 /vendor/data/GeoLite2-City.mmdb
 
-# Vagrant
+# Front-end
-.vagrant
+dist
+node_modules
+yarn-error.log
 
-# ignore auto-generated plugin js assets
+# Auto-generated plugin JS assets
 /app/assets/javascripts/plugins/*
 
-# ignore generated api documentation files
+# Generated API documentation files
 openapi/*
-
-# ignore VSCode config files
-.vscode
-
-# ignore direnv
-.envrc
-
-# ember-cli generated
-dist
-
-# Copyright Deposits
-copyright
-
-yarn-error.log
-tags
-
-# file used with `discourse_dev` gem in development environment.
-config/dev.yml

bin/rubocop

@@ -0,0 +1,29 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'rubocop' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+bundle_binstub = File.expand_path("../bundle", __FILE__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("rubocop", "rubocop")