rebase: use cmdutil.check_at_most_one_arg() for --confirm/--dry-run

I've also updated the helper to work with the hyphenated --dry-run
option.

Differential Revision: https://phab.mercurial-scm.org/D7641

hgext/rebase.py

@@ -1026,8 +1026,7 b' def rebase(ui, repo, **opts):'
         raise error.Abort(_(b'cannot specify both --dry-run and --%s') % action)
     if confirm and action:
         raise error.Abort(_(b'cannot specify both --confirm and --%s') % action)
-    if dryrun and confirm:
-        raise error.Abort(_(b'cannot specify both --confirm and --dry-run'))
+    cmdutil.check_at_most_one_arg(opts, b'confirm', b'dry_run')
 
     if action or repo.currenttransaction() is not None:
         # in-memory rebase is not compatible with resuming rebases.

mercurial/cmdutil.py

@@ -268,6 +268,7 b' def check_at_most_one_arg(opts, *args):'
     previous = None
     for x in args:
         if opts.get(x):
+            x = x.replace(b'_', b'-')
             if previous:
                 raise error.Abort(
                     _(b'cannot specify both --%s and --%s') % (previous, x)