[mercurial]

Sure, but consider the common case of wanting the most recent file/directory in a directory. This would be something like "ls -t|head -n 1". It's pretty convenient, AND your ls function still returns only file and directory names, no additional information.

Here, you'd need to either parametrize the return type of ls to get simple strings (which is what you want most of time) or additional metadata, or alternatively to have different ls commands.