extdiff: add --from/--to and deprecate -r, as was done for `hg diff`...
extdiff: add --from/--to and deprecate -r, as was done for `hg diff`
I recently replaced `hg diff`'s `-r` flag by `--from` and `--to` and
then deprecated the `-r` flag. This patch repeats that for
`hg extdiff`.
Differential Revision:
https://phab.mercurial-scm.org/D9624
