copy: add experimental support for marking committed copies The simplest way I'm aware of to mark a file as copied/moved after committing is this: hg uncommit --keep <src> <dest> # <src> needed for move, but not copy hg mv --after <src> <dest> hg amend This patch teaches `hg copy` a `--at-rev` argument to simplify that into: hg copy --after --at-rev . <src> <dest> In addition to being simpler, it doesn't touch the working copy, so it can easily be used even if the destination file has been modified in the working copy. Differential Revision: https://phab.mercurial-scm.org/D8035

copy: move argument validation a little earlier Argument validation is usually done early and I will want it done before some code that I'm about to add. Differential Revision: https://phab.mercurial-scm.org/D8033