jgit clone (in our *.pgm package) wants this to decide on the default name for the local working directory if the argument wasn't supplied.  Its supposed to guess off the URL.

I could see any other GUI based on top of JGit wanting the same feature, that is, given a URIish obtain the default name for the local working directory off that URI just as git clone would do.  The UI probably should then use that to pre-populate a text field that the user can modify.

It makes sense to make this algorithm common, and part of URIish.  But anytime one would want to do this, you probably have a URIish on hand, which is why I lobbied for the instance method rather than the static variant.  I'm still not sure about the static variant.