Point to a tap when installing or fetching.

When installing or fetching and stuff goes wrong we can't always catch
the error and redirect to the tap. Instead, point to the tap before we
do anything failure-prone and hopefully that'll encourage people to
file issues in the right place. If not we can say that explicitly.

Closes Homebrew/homebrew#33220.

Library/Homebrew/cmd/fetch.rb

@@ -17,6 +17,8 @@ module Homebrew
 
     puts "Fetching: #{bucket * ', '}" if bucket.size > 1
     bucket.each do |f|
+      f.print_tap_action :verb => "Fetching"
+
       if fetch_bottle?(f)
         fetch_formula(f.bottle)
       else

Library/Homebrew/cmd/install.rb

@@ -102,6 +102,8 @@ module Homebrew
   end
 
   def install_formula f
+    f.print_tap_action
+
     fi = FormulaInstaller.new(f)
     fi.options             = f.build.used_options
     fi.ignore_deps         = ARGV.ignore_deps?

Library/Homebrew/formula.rb

@@ -408,6 +408,13 @@ class Formula
     end
   end
 
+  def print_tap_action options={}
+    if tap?
+      verb = options[:verb] || "Installing"
+      ohai "#{verb} #{name} from #{tap}"
+    end
+  end
+
   # True if this formula is provided by Homebrew itself
   def core_formula?
     path == Formula.path(name)