Im not sure it is tidy to inject random junk into your commit message to get a hash prefix

Or maybe it is _extremely_ tidy.

I think the question boils down to "where is the junk?" ;) I.e, there is always junk, some put it in a commit hash, others into the files committed.

And now this uses invisible junk (white space). See update: https://news.ycombinator.com/item?id=33704810