For the record, we do have tutorial-like documentation and document more than one way to do things in multiple places throughout the devguide.  For example:

http://docs.python.org/devguide/faq.html#how-do-i-list-the-files-in-conflict-after-a-merge

Unlike the short options for long commands, though, it's not obvious to look for something like `make -C` (because you don't already know it's there).  That's why I think this option is more deserving.

Personally, when working on doc patches, I frequently go back and forth between `make html` and `hg diff`.  Knowing about -C means one doesn't have to cd up and down the directory each time or double-check what directory one is in.

I think it's okay and should even be a goal of the devguide to point out more efficient ways to contribute, which may sometimes involve saying more than the minimum (e.g. saying how something works, or stating a more "advanced" way to do something).  I still think we should strive for conciseness within those constraints.  Here is a new patch that makes the current language more concise in addition to some other minor changes.