diff: add --from and --to flags as clearer alternative to -r -r I think it was mistake to let the `-r` flag accept two revisions in `hg diff` in 98633e60067c (Support for 0, 1, or 2 diff revs, 2005-05-07). The command clearly acts on two revisions and having a single flag to indicate which those are is unclear. It got worse when it started accepting revsets as input. This patch introduces `--from` and `--to` flags, each taking a single revision and each defaulting to the working copy. That means that `hg