RE: vc-dir default directory: repository root?

[Drew Adams]

> Putting a value in history that the user has never put in themselves
> means overloading the term "history".

Wow, flash from the past!  I offered that argument long ago.
But that ship sailed nearly as long ago.

`M-n' has long (now) meant either move forward in the history or
move forward among a list of default values.  IOW, Emacs has
prepended multiple default values to the history list for a long
time.

And this behavior is handy - my argument still makes sense, but
it is not the only consideration.

What might be even better would be some (optional) visual
indication when you cross the threshold between past inputs
and default values. IOW, make clear whether a given entry was
a past input or is a suggested (default) value.