[tensorproduct]

Actually, I thought of an analogy that helps me reason about this.

If we think of the VCS like a text editor, then a branch is like a file that you can write changes to. However, if you're working on an unnamed file, then the editor (or its designers) has to make a choice about what to do with that unnamed document when you're done.

Git treats an unnamed branch like the scratch buffer in Emacs. You can make all the changes you want, but once you close it, it's gone (in this case, eligible for GC). This seems reasonable, because if you cared about it, you would have given it a name.

Mercurial's designers work off a different assumption: all the work that you do is important (and it provides other mechanisms to allow rough work). So if you start working in an unnamed branch, that's no problem. You can have as many unnamed branches as you like, but it's up to you to remember your way around. Going back to the filesystem analogy, it becomes like navigating between your unnamed text files by their address on the disk, rather than a nice human readable name.

Does this analogy make sense to anybody else?