Fix race condition when auto-moving implications

app/models/tag_alias.rb

@@ -145,8 +145,14 @@ class TagAlias < ActiveRecord::Base
     implications.each do |ti|
       ti.antecedent_name = self.consequent_name
       success = ti.save
-      if !success && ti.errors.full_messages.join("; ") =~ /Cannot implicate a tag to itself/
+      if !success
-        ti.destroy
+        case ti.errors.full_messages.join("; ")
+        when /Cannot implicate a tag to itself/
+          ti.destroy
+        when /Consequent tag must not be aliased to another tag/
+          ti.consequent_name = TagAlias.to_aliased(ti.consequent_name).first
+          ti.save
+        end
       end
     end
 
@@ -154,8 +160,14 @@ class TagAlias < ActiveRecord::Base
     implications.each do |ti|
       ti.consequent_name = self.consequent_name
       success = ti.save
-      if !success && ti.errors.full_messages.join("; ") =~ /Cannot implicate a tag to itself/
+      if !success
-        ti.destroy
+        case ti.errors.full_messages.join("; ")
+        when /Cannot implicate a tag to itself/
+          ti.destroy
+        when /Antecedent tag must not be aliased to another tag/
+          ti.antecedent_name = TagAlias.to_aliased(ti.antecedent_name).first
+          ti.save
+        end
       end
     end
   end