Fix editor on Linux.

lib/tasks/fish.rake

@@ -2,6 +2,7 @@
 
 require 'add_line_to_file'
 require 'user'
+require 'macos'
 
 task :fish => [:'brew:casks_and_formulae'] do
   fish_executable = (which 'fish')
@@ -13,6 +14,15 @@ task :fish => [:'brew:casks_and_formulae'] do
     command sudo, '/usr/bin/chsh', '-s', fish_executable, USER
   end
 
+  editor = macos? ? 'mate' : 'code'
+
+  fish_conf_dir = Pathname('~/.config/fish/conf.d').expand_path
+  (fish_conf_dir/'editor.fish').write <<~FISH
+    set -x EDITOR '#{editor} -w'
+    set -x HOMEBREW_EDITOR '#{editor}'
+    alias edit='#{editor}'
+  FISH
+
   puts ANSI.blue { 'Installing Fish Plugins …' }
   plugins = %w[
     edc/bass