prevent Gollum::Wiki instances from creating new pages that overwrite pages with the same name.

lib/gollum.rb

@@ -58,5 +58,19 @@ module Gollum
       'img' => {'href' => ['http', 'https', :relative]}
     }
   }
+
+  class Error < StandardError; end
+  class DuplicatePageError < Error
+    attr_accessor :dir
+    attr_accessor :existing_path
+    attr_accessor :attempted_path
+
+    def initialize(dir, existing, attempted, message = nil)
+      @dir            = dir
+      @existing_path  = existing
+      @attempted_path = attempted
+      super(message || "Cannot write #{@dir}/#{@attempted_path}, found #{@dir}/#{@existing_path}.")
+    end
+  end
 end
 

lib/gollum/wiki.rb

@@ -315,13 +315,24 @@ module Gollum
       ext  = @page_class.format_to_ext(format)
       path = @page_class.cname(name) + '.' + ext
 
-      parts = dir.split('/')
+      parts     = dir.split('/')
       container = nil
       parts.each do |part|
         container = map[part]
       end
 
-      (container || map)[path] = normalize(data)
+      container ||= map
+      downpath    = path.downcase
+      downpath.sub! /\.\w+$/, ''
+      container.keys.each do |existing|
+        file = existing.downcase
+        file.sub! /\.\w+$/, ''
+        if downpath == file
+          raise DuplicatePageError.new(dir, existing, path)
+        end
+      end
+
+      container[path] = normalize(data)
       map
     end