[examples/rename] Improve comments.

examples/rename.lua

@@ -21,6 +21,7 @@ local pattern = assert(select(1, ...), "Missing filename pattern argument")
 local repl = assert(select(2, ...), "Missing filename replacement argument")
 local path = select(3, ...) or "."
 
+-- Rename en-masse
 for filename in dir(path) do
     local newfilename = filename:gsub(pattern, repl, 1)
 
@@ -28,14 +29,17 @@ for filename in dir(path) do
         local from = path..sep..filename
         local to = path..sep..newfilename
 
+        -- Refuse to overwrite files
         local buf, err, code = osx.stat(to)
         if buf then
             error(filename..": File '"..to.."' exists, refusing to overwrite.")
         end
         if code ~= ENOENT then
+            -- Anything but "file does not exist" is dangerous, so bail out
             error(err)
         end
 
+        -- Print a nice message and rename things
         write(from, ' -> ', to)
         assert(osx.rename(filename, newfilename))
     end