Added --dry-run to unlink

Closes Homebrew/homebrew#43561.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/cmd/unlink.rb

@@ -1,12 +1,23 @@
+require "ostruct"
+
 module Homebrew
   def unlink
     raise KegUnspecifiedError if ARGV.named.empty?
 
+    mode = OpenStruct.new
+    mode.dry_run = true if ARGV.dry_run?
+
     ARGV.kegs.each do |keg|
+      if mode.dry_run
+        puts "Would remove:"
+        keg.unlink(mode)
+        next
+      end
+
       keg.lock do
         print "Unlinking #{keg}... "
         puts if ARGV.verbose?
-        puts "#{keg.unlink} symlinks removed"
+        puts "#{keg.unlink(mode)} symlinks removed"
       end
     end
   end

Library/Homebrew/keg.rb

@@ -186,7 +186,7 @@ class Keg
     remove_oldname_opt_record
   end
 
-  def unlink
+  def unlink(mode = OpenStruct.new)
     ObserverPathnameExtension.reset_counts!
 
     dirs = []
@@ -201,6 +201,11 @@ class Keg
 
         # check whether the file to be unlinked is from the current keg first
         if dst.symlink? && src == dst.resolved_path
+          if mode.dry_run
+            puts dst
+            next
+          end
+
           dst.uninstall_info if dst.to_s =~ INFOFILE_RX
           dst.unlink
           Find.prune if src.directory?
@@ -208,9 +213,10 @@ class Keg
       end
     end
 
+    unless mode.dry_run
       remove_linked_keg_record if linked?
-
       dirs.reverse_each(&:rmdir_if_possible)
+    end
 
     ObserverPathnameExtension.total
   end